Display device and manufacturing method of the same

ABSTRACT

It is an object of the present invention to provide a method for manufacturing a display device in which unevenness generated under a light-emitting element does not impart an adverse effect on the light-emitting element. It is another object of the invention to provide a method for manufacturing a display device in which penetration of water into the inside of the display device through a film having high moisture permeability can be suppressed without increasing processing steps considerably. A display device of the present invention comprises a thin film transistor and a light-emitting element, the light-emitting element including a light-emitting laminated body interposed between a first electrode and a second electrode; wherein the first electrode is formed over an insulating film formed over the thin film transistor; and wherein a planarizing film is formed in response to the first electrode between the first electrode and the insulating film.

BACKGROUND OF THE INVENTION

The present invention relates to a method for manufacturing a displaydevice using an element emitting light (light-emitting element) byapplying current between electrodes interposing a light-emittingmaterial therebetween.

DESCRIPTION OF RELATED ART

In recent years, a thin lightweight display using a light-emittingelement has been actively developed. The light-emitting element ismanufactured by interposing a material which emits light by applyingcurrent between a pair of electrodes. Since the light-emitting elementitself emits light unlike in the case of liquid crystal, a light sourcesuch as a backlight is not required, and the element is very thin.Therefore, it is extremely advantageous to manufacture a thinlightweight display.

However, one background of not reaching practical use yet while havingsuch big advantages is a problem of reliability. The light-emittingelement using an organic-based material often deteriorates due tomoisture (water) and has a disadvantage of being hard to obtainlong-term reliability. The light-emitting element which is deteriorateddue to water causes a decrease in luminance or does not emit light. Itis conceivable that this causes a dark spot (black spot) and shrinkage(decrease in luminance from an edge portion of a display device) in adisplay device using the light-emitting element. Various countermeasuresare suggested to suppress such deterioration (refer to Patent Document 1and Patent Document 2, for example).

However, these countermeasures are not enough to obtain sufficientreliability of the light-emitting element; thus, it is desired tofurther improve the reliability.

In addition, since a thin film light-emitting element is formed bylaminating extremely thin films, the film and wiring covering an unevenportion is cut due to unevenness under the light-emitting element, whichcauses a defect.

-   Patent Document 1: Japanese Patent Laid-Open No. H9-148066-   Patent Document 2: Japanese Patent Laid-Open No. H7-169567

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In order to suppress the above defects, it is sufficient that unevennessunder the light-emitting element is relieved; therefore, a planarizingfilm is formed over the surface on which unevenness exists.

However, an insulating film used for such a planarizing film often hashigh moisture permeability; therefore, there is a risk that waterpenetrates through the insulating film into the inside of a displaydevice by exposing the insulating film to external atmosphere. Inaddition, if the insulating film is removed by etching or the like so asnot to be exposed to external atmosphere, a new mask is needed, whichcauses an increase in processing steps, and the problem can not bedisregarded.

Considering the above facts, it is an object of the present invention toprovide a method for manufacturing a display device in which unevennessgenerated under a light-emitting element does not impart an adverseeffect on the light-emitting element. It is another object of theinvention to provide a method for manufacturing a display device inwhich penetration of water into the inside of the display device througha film having high moisture permeability can be suppressed withoutincreasing processing steps considerably. It is another object of theinvention to provide a method for manufacturing a display devicesatisfying the above two simultaneously.

Means for Solving the Problem

A display device of the present invention to solve the above problemsincludes a thin film transistor and a light-emitting element over aninsulating surface formed on a substrate, wherein the light-emittingelement includes a light-emitting laminated body interposed between afirst electrode and a second electrode; wherein the first electrode isformed over an insulating film formed over the thin film transistor; andwherein a planarizing film is disposed so as to correspond to at least aposition of the first electrode between the first electrode and theinsulating film.

A display device of the present invention to solve the above problemsincludes a thin film transistor and a light-emitting element over aninsulating surface on a substrate, wherein the light-emitting elementincludes a light-emitting laminated body interposed between a firstelectrode and a second electrode; wherein the first electrode is formedover a first insulating film formed over the thin film transistor;wherein a planarizing film is disposed in response to at least aposition of the first electrode at least between the first electrode andthe insulating film; and wherein the planarizing film is not formedoutside a sealant forming region of the substrate.

A method for manufacturing a display device of the present invention tosolve the above problems, includes the steps of: forming a semiconductorfilm, a gate insulating film, and a gate electrode over an insulatingsurface; forming a first insulating film over the gate electrode;forming a contact hole reaching to the semiconductor film by etching thegate insulating film and the first insulating film; forming a conductivefilm electrically connected to the semiconductor film over the firstinsulating film; forming a second insulating film covering the firstinsulating film and the conductive film with the use of a materialhaving a self-planarizing property; exposing at least part of theconductive film by etching the second insulating film; forming a pixelelectrode electrically connected to the conductive film; removing aregion of the second insulating film not covered with the pixelelectrode with the use of the pixel electrode as a mask by etching; andforming a light-emitting element having the pixel electrode as oneelectrode.

A method for manufacturing a display device of the present invention tosolve the above problems, includes the steps of: forming a semiconductorfilm over an insulating surface; forming a gate insulating film coveringthe semiconductor film; forming a gate electrode over the gateinsulating film and the semiconductor film; forming a first insulatingfilm covering the gate insulating film and the gate electrode; forming asecond insulating film covering the first insulating film with the useof a material having a self-planarizing property; forming a pixelelectrode over the second insulating film; removing a region of thesecond insulating film not covered with the pixel electrode with the useof the pixel electrode as a mask by etching; forming a contact holereaching to the semiconductor film in the first insulating film and thegate insulating film; forming a wiring electrically connected to thesemiconductor film through the contact hole over the first insulatingfilm; and forming a light-emitting element in which part of the wiringis also electrically connected to the pixel electrode and having thepixel electrode as one electrode.

A method for manufacturing a display device of the present invention tosolve the above problems, includes the steps of: forming a semiconductorfilm over an insulating surface; forming a gate insulating film coveringthe semiconductor film; forming a gate electrode over the gateinsulating film and the semiconductor film; forming a first insulatingfilm covering the gate insulating film and the gate electrode; forming asecond insulating film covering the first insulating film with the useof a material having a self-planarizing property; forming a pixelelectrode over the second insulating film; forming a contact holereaching to the semiconductor film in the second insulating film, thefirst insulating film, and the gate insulating film; forming aconductive film electrically connected to the semiconductor film throughthe contact hole over the second insulating film; removing a region ofthe second insulating film not covered with the conductive film and thepixel electrode with the use of the conductive film and the pixelelectrode as masks by etching; and forming a light-emitting element inwhich part of the conductive film is also electrically connected to thepixel electrode and having the pixel electrode as one electrode.

A method for manufacturing a display device of the present invention tosolve the above problems, includes the steps of: forming a semiconductorfilm over an insulating surface; forming a gate insulating film coveringthe semiconductor film; forming a gate electrode over the gateinsulating film and the semiconductor film; forming a first insulatingfilm covering the gate insulating film and the gate electrode; forming asecond insulating film covering the first insulating film with the useof a material having a self-planarizing property; forming a contact holereaching to the semiconductor film in the second insulating film, thefirst insulating film, and the gate insulating film; forming aconductive film electrically connected to the semiconductor film throughthe contact hole over the second insulating film; forming a pixelelectrode overlapped with at least part of the conductive film over thesecond insulating film; and forming a light-emitting element having thepixel electrode as one electrode.

A method for manufacturing a display device of the present invention tosolve the above problems, includes the steps of: forming a semiconductorfilm, a gate insulating film and a gate electrode over an insulatingsurface formed on a substrate; forming a first insulating film coveringthe gate electrode; forming a contact hole reaching to the semiconductorfilm by etching the gate insulating film and the first insulating film;forming a conductive film electrically connected to the semiconductorfilm through the contact hole over the first insulating film; forming asecond insulating film over the first insulating film and the conductivefilm with the use of a material having a self-planarizing property;exposing at least part of the conductive film by etching the secondinsulating film; forming a third insulating film covering the secondinsulating film and the exposed portion of the conductive film; forminga mask over the third insulating film; forming a contact hole reachingto the conductive film by etching, and removing the second insulatingfilm in an edge portion of the substrate with the use of the mask byetching; forming a pixel electrode electrically connected to theconductive film through the contact hole; and forming a light-emittingelement having the pixel electrode as one electrode.

A method for manufacturing a display device of the present invention tosolve the above problems, includes the steps of: forming a semiconductorfilm, a gate insulating film, and a gate electrode over an insulatingsurface; forming a first insulating film over the gate electrode;forming a contact hole reaching to the semiconductor film by etching thegate insulating film and the first insulating film; forming a firstconductive film electrically connected to the semiconductor film throughthe contact hole over the first insulating film; forming a secondinsulating film over the first insulating film and the first conductivefilm; forming a contact hole reaching to the first conductive film byetching the second insulating film; forming a second conductive filmelectrically connected to at least part of the first conductive film;forming a third insulating film covering the second insulating film andthe second conductive film with the use of a material having aself-planarizing property; exposing at least part of the secondconductive film by etching the third insulating film; forming a pixelelectrode electrically connected to the second conductive film over thethird insulating film with the use of a mask; removing a region of thethird insulating film not covered with the mask and the pixel electrodewith the use of the mask and the pixel electrode as masks by etching;and forming a light-emitting element having the pixel electrode as oneelectrode.

A method for manufacturing a display device of the present invention tosolve the above problems, includes the steps of: forming a semiconductorfilm over an insulating surface; forming a gate insulating film coveringthe semiconductor film; forming a gate electrode over the gateinsulating film and the semiconductor film; forming a first insulatingfilm covering the gate insulating film and the gate electrode; forming acontact hole reaching to the semiconductor film in the first insulatingfilm and the gate insulating film; forming a first conductive filmelectrically connected to the semiconductor film through the contacthole over the first insulating film; forming a second insulating filmcovering the first insulating film and the first conductive film;forming a third insulating film covering the second insulating film withthe use of a material having a self-planarizing property; forming apixel electrode over the third insulating film with the use of a mask;removing a region of the third insulating film not covered with the maskand the pixel electrode with the use of the mask and the pixel electrodeas masks by etching; forming a contact hole reaching to the firstconductive film in the second insulating film; forming a secondconductive film electrically connected to the first conductive filmthrough the contact hole over the second insulating film; and forming alight-emitting element in which part of the second conductive film isalso electrically connected to the pixel electrode and having the pixelelectrode as one electrode.

A method for manufacturing a display device of the present invention tosolve the above problems, includes the steps of: forming a semiconductorfilm over an insulating surface; forming a gate insulating film coveringthe semiconductor film; forming a gate electrode over the gateinsulating film and the semiconductor film; forming a first insulatingfilm covering the gate insulating film and the gate electrode; forming acontact hole reaching to the semiconductor film in the first insulatingfilm and the gate insulating film; forming a first conductive filmelectrically connected to the semiconductor film through the contacthole over the first insulating film; forming a second insulating filmcovering the first insulating film and the first conductive film;forming a third insulating film covering the second insulating film withthe use of a material having a self-planarizing property; forming apixel electrode over the third insulating film with the use of a mask;forming a contact hole reaching to the first conductive film in thethird insulating film and the second insulating film; forming a secondconductive film electrically connected to the first conductive filmthrough the contact hole over the third insulating film with the use ofa mask; removing a region of the third insulating film not covered withthe pixel electrode and the second conductive film with the use of thepixel electrode and the second conductive film as masks; and forming alight-emitting element having the pixel electrode as one electrode.

A method for manufacturing a display device of the present invention tosolve the above problems, includes the steps of: forming a semiconductorfilm over an insulating surface; forming a gate insulating film coveringthe semiconductor film; forming a gate electrode over the gateinsulating film and the semiconductor film; forming a first insulatingfilm covering the gate insulating film and the gate electrode; forming acontact hole reaching to the semiconductor film in the first insulatingfilm and the gate insulating film; forming a first conductive filmelectrically connected to the semiconductor film through the contacthole over the first insulating film; forming a second insulating filmcovering the first insulating film and the first conductive film;forming a extremely thin third insulating film covering the secondinsulating film with the use of a material having a self-planarizingproperty; forming a contact hole reaching to the first conductive filmin the third insulating film and the second insulating film; forming asecond conductive film electrically connected to the first conductivefilm through the contact hole over the third insulating film with theuse of a mask; forming a pixel electrode in contact with the secondconductive film; and forming a light-emitting element having the pixelelectrode as one electrode.

Effect of the Invention

In accordance with a method for manufacturing a display device of thepresent invention, a light-emitting device in which unevenness generatedunder a light-emitting element does not impart an adverse effect on thelight-emitting element can be manufactured. Further, a light-emittingdevice in which penetration of water into the inside of thelight-emitting device through a film having high moisture permeabilitycan be suppressed without increasing processing steps considerably canbe manufactured. Furthermore, a light-emitting device satisfying theabove two simultaneously can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1E Diagrams showing a method for manufacturing a display deviceof the present invention (Embodiment Mode 1).

FIGS. 2A-2E Diagrams showing a method for manufacturing a display deviceof the invention (Embodiment Mode 1).

FIGS. 3A-3D Diagrams showing a method for manufacturing a display deviceof the invention (Embodiment Mode 1).

FIGS. 4A-4B Diagrams showing a method for manufacturing a display deviceof the invention (Embodiment Mode 1).

FIGS. 5A-5E Diagrams showing a method for manufacturing a display deviceof the invention (Embodiment Mode 2).

FIGS. 6A-6D Diagrams showing a method for manufacturing a display deviceof the invention (Embodiment Mode 2).

FIGS. 7A-7E Diagrams showing a method for manufacturing a display deviceof the invention (Embodiment Mode 3).

FIGS. 8A-8C Diagrams showing a method for manufacturing a display deviceof the invention (Embodiment Mode 3).

FIGS. 9A-9E Diagrams showing a method for manufacturing a display deviceof the invention (Embodiment Mode 4).

FIGS. 10A-10C Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 4).

FIGS. 11A-11D Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 5).

FIGS. 12A-12C Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 5).

FIGS. 13A-13D Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 6).

FIGS. 14A-14C Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 6).

FIGS. 15A-15D Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 7).

FIGS. 16A-16D Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 7).

FIGS. 17A-17D Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 8).

FIGS. 18A-18C Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 8).

FIGS. 19A-19D Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 9).

FIGS. 20A-20D Diagrams showing a method for manufacturing a displaydevice of the invention (Embodiment Mode 9).

FIGS. 21A-21D Diagrams showing an example of a light-emitting devicemanufactured by a method for manufacturing a display device of theinvention (Embodiment Modes 1 to 4).

FIGS. 22A-22D Diagrams showing an example of a liquid crystal displaydevice manufactured by a method for manufacturing a display device ofthe invention (Embodiment Modes 1 to 4).

FIGS. 23A-23E Diagrams showing an example of an electronic devicemounting a display device manufactured by a method for manufacturing adisplay device of the invention.

FIGS. 24A-24B Diagrams exemplifying one structure of a panel mounting adisplay device manufactured by a method for manufacturing a displaydevice of the invention.

FIGS. 25A-25F Diagrams showing an example of a pixel circuit mounted ona display device.

FIG. 26 A diagram showing an example of a protective circuit mounted ona display device.

DETAILED DESCRIPTION OF THE INVENTION Best Mode for Carrying Out theInvention

Hereinafter, an Embodiment Mode of the present invention will bedescribed with reference to the attached drawings. However, theinvention can be carried out with many different modes. As is easilyknown to a person skilled in the art, the mode and the detail of theinvention can be variously changed without departing from the purposeand the scope of the invention. Thus, the invention is not interpretedwhile limiting to the following description of the Embodiment Modes.

Embodiment Mode 1

A method for manufacturing a display device of the present inventionwill be described with reference to FIGS. 1 to 4.

First, a first base insulating film 101 and a second base insulatingfilm 102 are formed over a substrate 100, and a semiconductor layer isthen formed over the second base insulating film 102. The semiconductorlayer is etched with the use of masks 105 and 106 of photoresist or thelike in order to form island-shaped semiconductor layers 103 and 104(FIG. 1A).

Glass, quartz, plastic (such as polyimide, acrylic, polyethyleneterephthalate, polycarbonate, polyacrylate, or polyethersulfone), or thelike can be used as a material of the substrate 100. The substratethereof may be used after being polished by CMP or the like, ifnecessary. In this Embodiment Mode, a glass substrate is used.

The first base insulating film 101 and the second base insulating film102 are formed in order to prevent an element imparting an adverseeffect on characteristics of a semiconductor layer, such as alkali metalor alkali-earth metal contained in the substrate 100, from diffusinginto the semiconductor layers 103 and 104. Silicon oxide, siliconnitride, silicon oxide containing nitrogen, silicon nitride containingoxygen, or the like can be used as a material thereof. In thisEmbodiment Mode, the first base insulating film 101 and the second baseinsulating film 102 are formed from silicon nitride and silicon oxide,respectively. In this Embodiment Mode, although a base insulating filmis formed in two layers of the first base insulating film 101 and thesecond base insulating film 102, the base insulating film can be formedto be a single layer or to have a laminated structure of two or morelayers. Note that a base insulating film is not necessarily required tobe formed when diffusion of impurities from a substrate need not beworried about.

The subsequently formed semiconductor layer is obtained by performinglaser crystallization on an amorphous silicon film in this EmbodimentMode. An amorphous silicon film is formed to be 25 to 100 nm (preferably30 to 60 nm) in thickness over the second base insulating film 102. Aknown method such as a sputtering method, a low pressure CVD method, ora plasma CVD method can be used as a manufacturing method thereof.Subsequently, heat treatment is performed at a temperature of 500° C.for one hour for dehydrogenation of the thus formed silicon film.

Then, the amorphous silicon film is crystallized with the use of a laserirradiation apparatus to form a crystalline silicon film. As to thelaser crystallization in this Embodiment Mode, an excimer laser is used,and an emitted laser beam is processed to have a linear beam spot withan optical system. The amorphous silicon film is irradiated therewith tobe a crystalline silicon film, and is used as the semiconductor layer.

As another method for crystallizing an amorphous silicon film, there isa crystallizing method only by heat treatment or a crystallizing methodby heat treatment with the use of a catalytic element which promotescrystallization. Nickel, iron, palladium, tin, lead, cobalt, platinum,copper, gold, or the like can be used as the element which promotescrystallization. By using the above element, crystallization can beperformed at a lower temperature in a shorter time, compared to the caseof performing crystallization only by heat treatment. Therefore, a glasssubstrate or the like is less damaged. In the case of performingcrystallization only by heat treatment, a highly heat resistant quartzsubstrate or the like may be used as the substrate 100.

Subsequently, addition of a very small amount of impurities, so-calledchannel doping, is performed on the semiconductor layer to control athreshold value of gate voltage in a transistor, if necessary. An N typeor a P type impurity (phosphorus, boron, or the like) is added by an iondoping method to obtain a required threshold value.

Thereafter, the semiconductor layer is patterned to have a predeterminedshape as shown in FIG. 1A, thereby obtaining the island-shapedsemiconductor layers 103 and 104. The patterning is performed asfollows: a photoresist is applied to the semiconductor layer, exposed tolight and developed to form predetermined shapes of masks, and thenbaked to form the masks over the semiconductor layer; thereafter,etching is performed using the masks 105 and 106.

A gate insulating film 107 is formed to cover the semiconductor layers103 and 104. Subsequently, a first conductive film 108 and a secondconductive film 109 are formed over the gate insulating film 107 (FIG.1B). The gate insulating film 107 is formed to be 40 to 150 nm inthickness with an insulating film containing silicon by a plasma CVDmethod or a sputtering method. In this Embodiment Mode, silicon oxide isused.

The first conductive film 108 and the second conductive film 109 may beformed by using an element of tantalum, tungsten, titanium, molybdenum,aluminum, copper, chromium, or niobium or by using an alloy material ora compound material which mainly contains the above element. Asemiconductor film typified by a polycrystalline silicon film doped withan impurity element such as phosphorus may also be used. Alternatively,an AgPdCu alloy may be used.

Subsequently, gate electrodes are formed in positions overlapped withpart of the semiconductor layers 103 and 104 over the gate insulatingfilm 107 by etching the first conductive film 108 and the secondconductive film 109 (FIG. 1C). In this Embodiment Mode, as the firstconductive film 108, tantalum nitride (TaN) is formed to be 30 nm inthickness over the gate insulating film 107, and as the secondconductive film 109, tungsten (W) is formed to be 370 nm in thicknessthereover. Note that, although the first conductive film 108 is formedfrom TaN to be 30 nm in thickness, and the second conductive film 109 isformed from W to be 370 nm in thickness in this Embodiment Mode, thefirst conductive film 108 may be formed in the range of 20 to 100 nm inthickness, and the second conductive film 109 may be formed in the rangeof 100 to 400 nm in thickness. In addition, although a laminatedstructure of two layers is used in this Embodiment Mode, a single layeror a laminated structure of three or more layers may be used.

Masks 114 and 115 of resist or the like are formed through alight-exposure step by photolithography in order to form the gateelectrodes and a wiring by etching the first conductive film 108 and thesecond conductive film 109. In a first etching, etching is performedtwice using a first etching condition and a second etching condition.Etching conditions may be suitably selected. The following method isused for etching in this Embodiment Mode.

In the first etching, an ICP (inductively coupled plasma) etching methodis used. As the first etching condition, CF₄, Cl₂, and O₂ are used asetching gases of which gas flow rates are respectively 17/17/10, andplasma is generated with a pressure of 1.5 Pa by applying an RF (13.56MHz) power of 500 W to a coil type electrode in order to performetching. A substrate side (sample stage) is also applied with an RF(13.56 MHz) power of 120 W; thus, negative self-bias voltage issubstantially applied. By the first etching condition, the W film isetched so that an edge portion of the first conductive film has atapered shape.

Subsequently, etching is performed after moving to the second etchingcondition. With the masks of resist or the like remaining, etching isperformed for approximately 17 seconds by using CF₄ and Cl₂ as etchinggases of which gas flow rates are respectively 20/20, and by applying anRF (13.56 MHz) power of 500 W to a coil type electrode with a pressureof 1.5 Pa to generate plasma. A substrate side (sample stage) is alsoapplied with an RF (13.56 MHz) power of 10 W; thus, negative self biasvoltage is substantially applied. Under the second etching conditionmixing CF₄ and Cl₂, both of the W film and the TaN film are etched tothe same extent. In this first etching, edge portions of the firstconductive films 110, 111 and the second conductive films 112, 113 areeach formed into a tapered shape by an effect of the bias voltagesapplied to the substrate sides.

Subsequently, a second etching is performed without removing the masksof resist or the like (FIG. 1D). In the second etching, etching isperformed for approximately 25 seconds by using SF₆, Cl₂, and O₂ asetching gases of which gas flow rates are respectively 16/8/30, and byapplying an RF (13.56 MHz) power of 700 W to a coil side electrode witha pressure of 2.0 Pa to generate plasma. A substrate side (sample stage)is also applied with an RF (13.56 MHz) power of 10 W, thus negativeself-bias voltage is substantially applied. In this etching condition,the W film is selectively etched to form a conductive film in a secondshape. At this time, the first conductive film is slightly etched. Bythe first and second etchings, gate electrodes formed of the firstconductive films 116, 117 and the second conductive films 118, 119 areformed.

Without removing the masks of resist or the like, a first doping isperformed. By the first doping, impurities which impart an N type to thecrystalline semiconductor layers are lightly doped. The first doping maybe performed by an ion doping method or an ion implantation method. Acondition for the ion doping may be set with a dosage of 1×10¹³ to5×10¹⁴ atoms/cm² and an acceleration voltage of 40 to 80 kV. In thisEmbodiment Mode, the acceleration voltage is 50 kV. As an impurityelement which imparts an N type, an element belonging to a group 15 ofthe periodic table, typically phosphorus (P) or arsenic (As), can beused. In this Embodiment Mode, phosphorus (P) is used. Accordingly,first impurity regions 120 and 121 (N⁻⁻ region) doped with impurities atlaw concentrations are formed in self-alignment with the use of thefirst conductive films 116 and 117 as masks.

Subsequently, the masks 114 and 115 of resist or the like are removed.Then, a mask 122 is formed of resist or the like and a second doping isperformed at a higher acceleration voltage than in the first doping(FIG. 1E). Also in this second doping, impurities which impart an N typeare doped. A condition for the ion doping may be set with a dosage of1×10¹³ to 3×10¹⁵ atoms/cm² and an acceleration voltage of 60 to 120 kV.In this Embodiment Mode, the dosage is 3.0×10¹⁵ atoms/cm² and theacceleration voltage is 65 kV. The second doping is performed so thatthe semiconductor layers under the first conductive films 116 and 117are also doped with impurity elements with the use of the secondconductive films 118 and 119 as masks for the impurity elements.

By performing the second doping, a second impurity region 124 (N⁻region, Lov region) is formed in a portion of the semiconductor layersoverlapped with the first conductive films 116 and 117 but notoverlapped with the second conductive films 118 and 119 or in a portionnot covered with the mask. The second impurity region 124 is doped withimpurities which impart an N type in a concentration range from 1×10¹⁸to 5×10¹⁹ atoms/cm³. In addition, a portion of the semiconductor layernot covered with the first conductive film nor the mask (third impurityregion 123: N⁺ region) is doped with impurities which impart an N typeat a high concentration in the range of 1×10¹⁹ to 5×10²¹ atoms/cm³.

Each of the impurity regions is formed by doping twice in thisEmbodiment Mode; however, the invention is not limited to this. Dopingmay be performed once or multiple times to form an impurity regionhaving a desired impurity concentration by suitably setting a condition.

Next, the mask of resist or the like is removed, then, a mask 125 isformed of resist or the like to perform a third doping (FIG. 2A). Bythis third doping, the semiconductor layer to be a P-channel TFT isdoped with an impurity element which imparts an opposite conductivitytype to the first and second conductivity types in order to form afourth impurity region 126 (P⁺ region) and a fifth impurity region 127(E region).

In the third doping, the fourth impurity region 126 (P⁺ region) isformed in a portion not covered with the mask 125 of resist or the likenor overlapped with the first conductive film 117, and the fifthimpurity region 127 (E region) is formed in a portion not covered withthe mask of resist or the like but overlapped with the first conductivefilm, and not overlapped with the second conductive film. As an impurityelement which imparts a P type, an element belonging to a group 13 ofthe periodic table, such as boron (B), aluminum (Al), or gallium (Ga) isknown.

In this embodiment, the fourth and fifth impurity regions 126 and 127are formed with boron (B) as the P type impurity element by an iondoping method using diborane (B₂H₆). A condition for the ion doping isset with a dosage of 1×10¹⁶ atoms/cm² and an acceleration voltage of 80kV.

Note that the semiconductor layer to form an N-channel TFT is coveredwith the mask 125 of resist or the like in the third doping.

Here, the fourth impurity region 126 (P⁺ region) and the fifth impurityregion 127 (P⁻ region) are doped with phosphorus at differentconcentrations by the first and second dopings. However, the thirddoping is performed so that each of the fourth impurity region 126 (P⁺region) and the fifth impurity region 127 (E region) contains theimpurity element which imparts a P type at a concentration of 1×10¹⁹ to5×10²¹ atoms/cm². Therefore, the fourth impurity region (P⁺ region) andthe fifth impurity region (P⁻ region) function as source and drainregions of the P-channel TFT without problems.

In this Embodiment Mode, the fourth impurity region 126 (P⁺ region) andthe fifth impurity region 127 (P⁻ region) are formed by performing thethird doping once; however, the invention is not limited to this. Dopingmay also be suitably performed multiple times to form the fourthimpurity region 126 (P⁺ region) and the fifth impurity region 127 (P⁻region) depending on a condition of the doping.

Consequently, a thin film transistor formed of a semiconductor layer, agate insulating film, and a gate electrode is formed. Further, a TFT 146(N-channel type) for a driver circuit portion formed of thesemiconductor layer 103, the gate insulating film 107, and the gateelectrodes 116 and 118 and a TFT 147 (P-channel type) for a pixelportion (for driving a light-emitting element) formed of thesemiconductor layer 104, the gate insulating film 107, and the gateelectrodes 117 and 119 are formed. Note that a manufacturing method of athin film transistor is not limited to this, and a known manufacturingmethod may be appropriately used. Further, the polarity of a TFT mayalso be freely designed by a user.

A top gate thin film transistor using a crystalline silicon filmcrystallized by laser crystallization is manufactured in this EmbodimentMode; however, a bottom gate thin film transistor using an amorphoussemiconductor film can be used for the pixel portion. Silicon germaniumas well as silicon can be used for an amorphous semiconductor. In thecase of using silicon germanium, the concentration of germanium ispreferably approximately 0.01 to 4.5 atomic %.

A microcrystalline semiconductor film (semi-amorphous semiconductor), inwhich a crystal grain of 0.5 to 20 nm can be observed within anamorphous semiconductor, may also be used. A microcrystal in which acrystal grain of 0.5 to 20 nm can be observed is also referred to as amicrocrystal (μc).

Semi-amorphous silicon (also referred to as SAS) that is asemi-amorphous semiconductor can be obtained by performing glowdischarge decomposition on a silicide gas. SiH₄ is typically used as thesilicide gas. In addition, Si₂H₆, SH₂Cl₂, SiHCl₃, SiCl₄, SiF₄, or thelike can also be used. The silicide gas can be diluted with hydrogen, orhydrogen and one or more rare gas elements of helium, argon, krypton,and neon, thereby making formation of the SAS easy. At this time, it ispreferable to dilute the silicide gas so that a dilution ratio rangesfrom 10 to 1000 times. Reaction production of the film by glow dischargedecomposition may be performed with a pressure in the range of 0.1 to133 Pa. A high-frequency power of 1 to 120 MHz, preferably 13 MHz to 60MHz, may be supplied to form a glow discharge. A substrate heatingtemperature is preferably 300° C. or less, and a recommended substrateheating temperature is in the range of 100 to 250° C.

In the thus formed SAS, a Raman spectrum is shifted to a lowerwavenumber side than 520 cm⁻¹. A diffraction peak of (111) or (220)caused by a crystal lattice of silicon is observed in X-ray diffraction.The SAS contains hydrogen or halogen of at least 1 atomic % or more toterminate a dangling bond. It is desirable that an atmosphericconstituent impurity such as oxygen, nitrogen, or carbon is 1×10²⁰/cm⁻¹or less as an impurity element in the film; in particular, an oxygenconcentration is 5×10¹⁹/cm³ or less, preferably 1×10¹⁹/cm³ or less. Whenthe SAS is processed into a TFT, μ=1 to 10 cm²/Vsec is given.

In addition, the SAS may be used by further crystallizing with a laser.

Subsequently, an insulating film (hydrogenated film) 128 is formed fromsilicon nitride to cover the gate electrodes and the gate insulatingfilm 107, and heat treatment is performed at 410° C. for about one hourin order to activate the impurity elements and hydrogenate thesemiconductor layers 103 and 104. Subsequently, an interlayer insulatingfilm 129 is formed to cover the insulating film (hydrogenated film) 128(FIG. 2B). As a material for forming the interlayer insulating film 129,an inorganic insulating film such as silicon oxide, silicon nitride, ora Low-k material may be used. In this Embodiment Mode, a silicon oxidefilm is formed as an interlayer insulating film.

Next, contact holes reaching to the semiconductor layers 103 and 104 areopened (FIG. 2C). The contact holes can be formed by etching with theuse of a mask 130 of resist or the like until the semiconductor layers103 and 104 are exposed. Either wet etching or dry etching can beemployed. Note that, etching may be performed once or in several batchesdepending on a condition. When etching is carried out in severalbatches, both wet etching and dry etching may be employed.

Next, a conductive film is formed to cover the contact holes and theinterlayer insulating film. The conductive film is processed into apredetermined shape using a mask 131 of resist or the like in order toform conductive films 132 to 136 to be a wiring, source or drainelectrodes, and the like, each of which is formed of the conductive film(FIG. 2D). This conductive film may be a single layer of a single metalsuch as aluminum or copper, a metal alloy typified by an aluminum alloysuch as an alloy of aluminum, carbon and titanium, an alloy of aluminum,carbon and nickel, or an alloy of aluminum, carbon and titanium, acompound, or the like. However, in this Embodiment Mode, the conductivefilm is a laminated structure of molybdenum, aluminum and molybdenum inthis order from the bottom. In addition, a laminated structure formed oftitanium, aluminum and titanium; titanium, titanium nitride, aluminumand titanium; titanium and an aluminum alloy, or the like may beemployed.

Thereafter, a planarizing film 137 is formed to cover the conductivefilms 132 to 136 and the interlayer insulating film 129 (FIG. 2E). As amaterial of the planarizing film 137, an application film with aself-planarizing property that can relieve unevenness formed in thelower layer by forming the film, for example, acrylic, polyimide, orsiloxane is preferably used. That is, a material that can form a filmhaving unevenness smaller than that formed in the lower layer can bepublicly employed. In addition, a film of which unevenness is relievedby reflowing or polishing the film once formed may be used. Hereinafter,these films are generally referred to as planarizing films. In thisEmbodiment Mode, the planarizing film 137 is formed from siloxane. Thisinsulating film having a self-planarizing property such as siloxane isapplied; thus, it is possible to relieve unevenness due to transferenceof ridges of the semiconductor layers 103 and 104, a slight unevennessof the interlayer insulating film, and unevenness of the lower layergenerated such as in forming the conductive films 132 to 136, and toperform planarization. Note that in this invention, siloxane is amaterial of which a skeleton structure is formed of the bond of siliconand oxygen, and in which an organic group containing at least hydrogen(such as an alkyl group or aryl group), a fluoro group, or an organicgroup containing at least hydrogen and a fluoro group may be used as thesubstituent.

Subsequently, etchback is performed on the planarizing film 137 in orderto expose the surface of the conductive film 136 as the drain electrodeof the TFT 147 for a pixel portion (for driving a light-emittingelement) (FIG. 3A). Consequently, contact with an electrode can berealized with the surface planarizing and without forming a new mask;thus, a defect caused by unevenness of the lower layer can be decreasedwithout increasing processing steps considerably.

Subsequently, a conductive film having a light transmitting property isformed to cover the planarizing film 137 and the exposed portion of theconductive film 136, and then a first electrode (anode) 140 of a thinfilm light-emitting element is formed by processing the conductive filmhaving a light transmitting property with the use of a mask 139 ofresist or the like by etching (FIG. 3B). Here, the first electrode(anode) 140 is electrically in contact with the conductive film 136. Asa material of the first electrode (anode) 140, metal, an alloy, anelectrically conductive compound each of which has high work function(work function of 4.0 eV or more), a mixture of these, or the like ispreferably used. For example, ITO (indium tin oxide), ITO containingsilicon (ITSO), IZO (indium zinc oxide) in which zinc oxide (ZnO) ismixed by 2 to 20 atomic % into indium oxide, zinc oxide, GZO (galliumzinc oxide) in which gallium is mixed into zinc oxide, gold (Au),platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum(Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or metalnitride (TiN) can be used. In this Embodiment Mode, ITSO is used as thefirst electrode (anode) 140.

After forming the first electrode (anode) 140, the planarizing film 137is removed by etching with the use of the first electrode (anode) 140and the mask 139 as masks without removing the mask 139 of resist or thelike (FIG. 3C). By removing the planarizing film 137 in this processingstep, the planarizing film corresponding to the first electrode (anode)140 remains; thus, planarization is realized under the first electrode(anode) 140, that is a portion in which the light-emitting element isformed; on the other hand, the planarizing film 137 corresponding to theother portion is removed. Therefore, the planarizing film is not exposedoutside a sealant forming region, and the planarizing film 137 is notexposed to external atmosphere. Consequently, penetration of water intothe inside of a panel through the planarizing film 137 is prevented, andit is possible to decrease deterioration of the light-emitting elementdue to water. In addition, the planarizing film 137 remains under thefirst electrode (anode) 140; thus, planarization is realized, and adefect caused by unevenness under the light-emitting element can bedecreased. Note that in this processing step, a new special mask is notrequired; the first electrode (anode) 140 and the mask 139 of resist orthe like used in manufacturing the anode are used. Therefore, it isunnecessary to further increase a processing step such asphotolithography, and planarization of the anode is realized withoutincreasing processing steps considerably.

A light-emitting device manufactured with the thus formed elementsubstrate in which the first electrode (anode) 140 is used as a firstelectrode of a light-emitting element has few defects caused byunevenness under the light-emitting element. Further, since water doesnot penetrate from external atmosphere through a planarizing film, thereliability is high. Note that it is desirable that unevenness of afirst electrode of a light-emitting element (first electrode (anode) 140in this Embodiment Mode) is 30 nm or less in a P−V value (maximumdifference of elevation) of one pixel, preferably 15 nm or less, morepreferably 10 nm or less. When the unevenness of the first electrodebelongs to the above range in the P−V value of one pixel, a defectincreasing with an accumulated drive time (emergence and expansion of anon-light-emitting region, hereinafter referred to as an increasing typedefect) can be greatly decreased.

Hereinafter, an example of a manufacturing method of a light-emittingelement and a display device using the first electrode (anode) 140fabricated by following this Embodiment Mode is shown. Needless to say,the manufacturing method of a light-emitting element and a displaydevice is not limited to this.

An insulating film is formed of an organic or inorganic material tocover the interlayer insulating film 129 and the first electrode (anode)140. Subsequently, the insulating film is processed to expose part ofthe first electrode (anode) 140, thereby forming a partition wall 141(FIG. 3D). As a material of the partition wall 141, a photosensitiveorganic material (acrylic, polyimide, or the like) is preferably used;however, a non-photosensitive organic material or an inorganic materialmay also be used. Further, the partition wall 141 may be used as a blackmatrix by making the partition wall 141 black in such a way that a blackpigment or dye such as titanium black or carbon nitride is diffused intothe material of the partition wall 141 with the use of a diffusematerial or the like. It is desirable that the partition wall 141 has atapered shape in its end surface toward the first electrode (anode) 140with its curvature changing continuously.

Note that it is desirable that an angle formed by the end surface of thepartition wall 141 toward the first electrode 140 side and the firstelectrode 140 is approximately 45±5°. Photosensitive polyimide is usedas the material of the partition wall 141 in order to obtain such ashape; specifically, the film thickness is approximately 1.0 μm, thetemperature of baking performed after exposing to light and developingfor patterning is approximately 300° C., thereby obtaining a preferableangle of approximately 43°. In addition, if exposure is performed on theentire surface again before baking is performed and after exposing tolight and developing for patterning, it is possible to make the anglesmaller.

Subsequently, a light-emitting laminated body 142 is formed to cover thefirst electrode (anode) 140 exposed from the partition wall 141. Thelight-emitting laminated body 142 may be formed by a vapor depositionmethod, a spin coating method, an ink-jet method, or the like.Subsequently, a second electrode (cathode) 143 is formed to cover thelight-emitting laminated body 142 (FIG. 4A). Accordingly, alight-emitting element including the first electrode (anode) 140, thelight-emitting laminated body 142, and the second electrode (cathode)143 can be manufactured. As a cathode material for forming the secondelectrode (cathode) 143, it is preferable to use metal, an alloy, anelectrically conductive compound, each of which has low work function(work function of 3.8 eV or less), a mixture of these, or the like. Notethat as specific examples of the cathode material, the followings can begiven: an element belonging to group 1 or 2 of the periodic table suchas Li or Cs, which are alkali metal, Mg, Ca, or Sr, which arealkali-earth metal; an alloy (Mg:Ag or Al:Li) or a compound (LiF, CsF,or CaF₂) containing the above element. In addition, the cathode can alsobe formed from transition metal containing rare-earth metal. Further, amultilayer formed of the above material and metal (including an alloy)such as Al, Ag, or ITO can be used. In this Embodiment Mode, the cathodeis formed from aluminum.

In addition, a buffer layer may be formed between a first electrode of alight-emitting element and a light-emitting laminated body.

When the first electrode of a light-emitting element is an anode, thebuffer layer is formed of a layer including both a hole-transportingmaterial and an electron-accepting material that can receive electronsfrom the hole-transporting material, a P type semiconductor layer, or alayer including a P type semiconductor. As the hole-transportingmaterial, an aromatic amine-based (having a bond of a benzene ring withnitrogen) compound, phthalocyanine (abbreviation: H2Pc), or aphthalocyanine compound such as copper phthalocyanine (abbreviation:CuPc) or vanadyl phthalocyanine (abbreviation: VOPc) can be used. Thearomatic amine-based compound is, for example,4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (abbreviation: α-NPD),4,4′-bis[N-(3-methylphenyl)-N-phenyl-amino]-biphenyl (abbreviation:TPD), 4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine (abbreviation:TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenyl-amino]-triphenylamine(abbreviation: MTDATA), or4,4′-bis(N-(4-(N,N-di-m-tolylamino)phenyl)-N-phenylamino)biphenyl(abbreviation: DNTPD). As the electron-accepting material that canreceive electrons from the above hole-transporting material, forexample, molybdenum oxide, vanadium oxide,7,7,8,8,-tetracyanoquinodimethane (abbreviation: TCNQ),2,3-dicyanonaphtoquinone (abbreviation: DCNNQ),2,3,5,6-tetrafluoro-7,7,8,8,-tetracyanoquinodimethane (abbreviation:F4-TCNQ), or the like is given. The electron-accepting material that canreceive electrons is selected in combination with the hole-transportingmaterial. Further, metal oxide such as molybdenum oxide, vanadium oxide,ruthenium oxide, cobalt oxide, nickel oxide, or copper oxide can be usedas the P type semiconductor.

When the first electrode of a light-emitting element is a cathode, thebuffer layer is formed of a layer including both anelectron-transporting material and an electron-donating material thatcan donate electrons to the electron-transporting material, an N typesemiconductor layer, or a layer including an N type semiconductor. Asthe electron-transporting material, for example, the following can beused: a material including a metal complex having a quinoline skeletonor a benzoquinoline skeleton, or the like such astris-(8-quinolinolato)aluminum (abbreviation: Alq₃),tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: BeBq₂), orbis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbreviation:BAlq). Besides the above, a material such as a metal complex having anoxazole or thiazole ligand, such asbis[2-(2-hydroxyphenyl)benzoxazolate]zinc (abbreviation: Zn(BOX)₂) orbis[2-(2-hydroxyphenyl)benzothiazolate]zinc (abbreviation: Zn(BTZ)₂),can be used. In addition to the metal complex,2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene(abbreviation: OXD-7),3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproin (abbreviation: BCP), or the like can be used. As theelectron donating material that can donate electrons to the aboveelectron-transporting material, for example, alkali metal such aslithium or cesium and its oxide, alkali-earth metal such as magnesium,calcium and its oxide, or rare-earth metal such as erbium or ytterbiumcan be used. The electron donating material that can donate electrons isselected in combination with the electron-transporting material.Further, a metal compound such as metal oxide can also be used as the Ntype semiconductor, and zinc oxide, zinc sulfide, zinc selenide,titanium oxide, or the like can be used.

The buffer layer formed of the above materials can further reduce theadverse effect of unevenness of the first electrode and further suppressan increasing type defect since it is possible for the buffer layer tobe a thick film without increasing the drive voltage much. When thebuffer layer is formed, assuming that it has a thickness of d nm, theP−V value of the first electrode of the light-emitting element in thepixel portion is 30 nm+d×0.2 nm or less, preferably 15 nm+d×0.2 nm orless, more preferably 10 nm+d×0.2 nm or less; therefore, it is possibleto relieve unevenness better.

Note that the buffer layer may also be formed between a second electrode(second electrode (cathode) 143 in this Embodiment Mode) and thelight-emitting laminated body.

Note that in this Embodiment Mode, the anode is electrically in contactwith the conductive film 136 to be the drain electrode of the drivingTFT for the light-emitting element. Alternatively, the cathode may beelectrically in contact with the conductive film 136.

Thereafter, a silicon oxide film containing nitrogen may be formed as apassivation film by a plasma CVD method. In the case of using thesilicon oxide film containing nitrogen, a silicon oxynitride film formedfrom SiH₄, N₂O, and NH₃, a silicon oxynitride film formed from SiH₄ andN₂O, or a silicon oxynitride film formed from a gas in which SiH₄ andN₂O are diluted with Ar may be deposited by a plasma CVD method.

Alternatively, a silicon oxynitride hydride film formed from SiH₄, N₂O,and H₂ may be used as the passivation film. Naturally, a structure ofthe passivation film is not limited to a single layer structure. Thepassivation film may have a laminated structure of another insulatingfilm containing silicon. In addition, a multilayer film of a carbonnitride film and a silicon nitride film, a multilayer film of styrenepolymer, a silicon nitride film, or a diamond like carbon film may beformed as a substitute.

The passivation film can suppress the entrance of elements which promotedeterioration of a light-emitting element from the top surface of thelight-emitting element; thus the reliability is improved.

Subsequently, in order to protect the light-emitting element from adeterioration-promoting material such as water, the display portion issealed (FIG. 4B). In the case of using an opposite substrate 145 forsealing, the opposite substrate is attached by an insulating sealingmaterial 144. The space between the opposite substrate 145 and theelement substrate may be filled with inert gas such as dry nitrogen;alternatively, the sealing material may be applied to the entire surfaceof the pixel portion for attaching the opposite substrate 145. It ispreferable to use an ultraviolet curable resin or the like as thesealing material 144. A drying agent or particles for keeping the gapbetween the substrates uniform may be mixed into the sealing material144.

A light-emitting device thus manufactured has few defects caused byunevenness under a light-emitting element. Further, a planarizing filmis not in contact with external atmosphere, and water does not penetratethrough the planarizing film; therefore, the light-emitting device hashigh reliability.

Further, the method for manufacturing a display device of the inventionis applied to a light-emitting device including a thin film transistorof another shape; the example is shown in FIG. 21A. The differencebetween FIG. 21A and FIG. 4B is the structures of the gate insulatingfilms and the shapes of the gate electrodes. In FIG. 21A, a gateinsulating film is formed of two layers: a first gate insulating film400 and a second gate insulating film 401. In addition, a gate electrode402 has a single layer structure having a tapered shape in its edgeportion. The first gate insulating film 400 is preferably formed of asilicon oxide-based film having a high insulating property and few traplevels since it is in contact with a semiconductor layer. In addition,forming the second gate insulating film 401 with a silicon nitride-basedfilm can make the operation stable even if the gate electrode 402 isformed from a material that is comparatively easy to be oxidized such asMo. In addition, a sealing material 144 is overlapped with an interlayerinsulating film 129.

Furthermore, an example of a liquid crystal display device manufacturedwith the method for manufacturing a display device of the invention isshown in FIG. 22A. After the liquid crystal display device ismanufactured up to the state shown in FIG. 3C, a spacer 301 is obtainedby forming an insulating film and patterning it. Thereafter, analignment film 302 is formed over the entire surface of the exposedportion, and then rubbing treatment is performed.

Subsequently, a sealing material 144 is formed by a droplet dischargemethod or the like, and then liquid crystal 300 is dropped and sealed inby an opposite substrate 306. A method for sealing in liquid crystal isdescribed below. A pattern of the sealing material 144 is made a closedpattern, and liquid crystal may be dropped by a liquid crystal droppingapparatus. Alternatively, an opening is formed in the pattern of thesealing material 144, and the opposite substrate 306 is attached;thereafter, a dip method (pumping up method) using a capillaryphenomenon may be employed. In addition, the sealing material 144 isoverlapped with an interlayer insulating film 129.

The opposite substrate 306 is provided with an opposite electrode 304and an alignment film 303 in this order from the opposite substrate 306side in advance.

The spacer 301 is formed by patterning the insulating film in FIG. 22A;however, a spherical spacer prepared separately may be dispersed overthe alignment film 302 in order to control a cell gap.

As described above, a liquid crystal display device can be completed byapplying the method for manufacturing a display device of the invention.

Embodiment Mode 2

A method for manufacturing a display device of the present invention,which is different from that of Embodiment Mode 1, will be describedwith reference to FIGS. 5 and 6. The processing steps are halfway thesame as those of Embodiment Mode 1; thus, the description and diagramsare omitted. Refer to Embodiment Mode 1. FIG. 5A corresponds to FIG. 2B.

After manufacturing up to the state shown in FIG. 5A followingEmbodiment Mode 1, a planarizing film 150 is formed to cover aninterlayer insulating film 129 (FIG. 5B). As a material of theplanarizing film 150, an application film with a self-planarizingproperty that can relieve unevenness formed in the lower layer byforming the film, for example, acrylic, polyimide, or siloxane ispreferably used. That is, a material that can form a film havingunevenness smaller than that formed in the lower layer can be publiclyemployed. In addition, a film of which unevenness is relieved byreflowing or polishing the film once formed may be used. In thisEmbodiment Mode, the planarizing film 150 is formed from siloxane. Thisinsulating film having a self-planarizing property such as siloxane isapplied; thus, it is possible to relieve unevenness due to a reflectionof ridges of semiconductor layers 103 and 104 or a slight unevenness ofthe interlayer insulating film, and to perform planarization.

Subsequently, a conductive film having a light transmitting property isformed to cover the planarizing film 150, and then a first electrode(anode) 152 of a thin film light-emitting element is formed byprocessing the conductive film having a light transmitting property withthe use of a mask 151 of resist or the like (FIG. 5C). A material of thefirst electrode (anode) 152 is the same as that of Embodiment Mode 1;thus, the description is omitted. Refer to Embodiment Mode 1. In thisEmbodiment Mode, ITO is used as the first electrode (anode) 152.

After forming the first electrode (anode) 152, the planarizing film 150is removed by etching with the use of the first electrode (anode) 152and the mask 151 as masks without removing the mask 151 of resist or thelike (FIG. 5D). By removing the planarizing film 150 in this processingstep, the planarizing film 150 corresponding to the first electrode(anode) 152 remains; thus, planarization is realized under the firstelectrode (anode) 152, which is a portion in which the light-emittingelement is formed; on the other hand, the planarizing film 150corresponding to the other portion is removed. Therefore, theplanarizing film is not exposed outside a sealant forming region, andthe planarizing film 150 is not exposed to external atmosphere.Consequently, penetration of water into the inside of a panel throughthe planarizing film 150 is prevented, and it is possible to decreasedeterioration of the light-emitting element due to water.

In addition, the planarizing film 150 remains under the first electrode(anode) 152 of the light-emitting element; thus, planarization isrealized in the first electrode, and a defect caused by unevenness underthe light-emitting element can be decreased. Note that it is desirablethat unevenness of the first electrode of the light-emitting element is30 nm or less in a P−V value of one pixel, preferably 15 nm or less,more preferably 10 nm or less. When the unevenness of the firstelectrode belongs to the above range in the P−V value of one pixel, anincreasing type defect can be greatly decreased.

In this processing step, a new special mask is not required; the firstelectrode (anode) 152 and the mask 151 of resist or the like used inmanufacturing the anode are used. Therefore, it is unnecessary tofurther increase a processing step such as photolithography, andplanarization of the anode is realized without increasing processingsteps considerably.

Next, contact holes reaching to the semiconductor layers 103 and 104 areopened (FIG. 5E). The contact holes can be formed by etching with theuse of a mask 153 of resist or the like until the semiconductor layers103 and 104 are exposed. Either wet etching or dry etching can beemployed. Note that, etching may be performed once or in several batchesdepending on a condition. When etching is carried out in severalbatches, both wet etching and dry etching may be employed.

Next, a conductive film is formed to cover the contact holes and theinterlayer insulating film. The conductive film is processed into apredetermined shape using a mask 154 of resist or the like in order toform conductive films 155 to 159 to be a wiring and source or drainelectrodes (FIG. 6A). This conductive film may be a single layer of asingle metal such as aluminum or copper, a metal alloy typified by analuminum alloy such as an alloy of aluminum, carbon and titanium, analloy of aluminum, carbon and nickel, or an alloy of aluminum, carbonand titanium, a compound, or the like. However, in this Embodiment Mode,this conductive film is a laminated structure of molybdenum, aluminumand molybdenum in this order of manufacture. In addition, a laminatedstructure formed of titanium, aluminum and titanium; titanium, titaniumnitride, aluminum and titanium; titanium and an aluminum alloy, or thelike may be employed. In addition, a conductive film 159 to be the drainelectrode of the driving TFT for the pixel portion is electrically incontact with the first electrode (anode) 152 that is a pixel electrode.

A light-emitting device manufactured with the thus formed elementsubstrate in which the first electrode (anode) 152 is used as a firstelectrode of a light-emitting element has few defects caused byunevenness under the light-emitting element. Further, since water doesnot penetrate from external atmosphere through a planarizing film, thereliability is high. Hereinafter, an example of a manufacturing methodof a light-emitting element and a display device using the firstelectrode (anode) 152 fabricated by following this Embodiment Mode isshown. Needless to say, the manufacturing method of a light-emittingelement and a display device is not limited to this.

An insulating film is formed of an organic or inorganic material tocover the interlayer insulating film 129 and the first electrode (anode)152. Subsequently, the insulating film is processed to expose part ofthe first electrode (anode) 152, thereby forming a partition wall 141(FIG. 6B). As a material of the partition wall 141, a photosensitiveorganic material (acrylic, polyimide, or the like) is preferably used;however, a non-photosensitive organic material or an inorganic materialmay also be used. Further, the partition wall 141 may be used as a blackmatrix by making the partition wall 141 black in such a way that a blackpigment or dye such as titanium black or carbon nitride is diffused intothe material of the partition wall 141 with the use of a diffusematerial or the like. It is desirable that the partition wall 141 has atapered shape in its end surface toward the first electrode (anode) 152with its curvature changing continuously.

Note that it is desirable that an angle formed by the end surface of thepartition wall 141 toward the first electrode 152 side and the firstelectrode 152 is approximately 45±5°. Photosensitive polyimide is usedas the material of the partition wall 141 in order to obtain such ashape; specifically, the film thickness is approximately 1.0 μm, thetemperature of baking performed after exposing to light and developingfor patterning is approximately 300° C., thereby obtaining a preferableangle of approximately 43°. In addition, if a processing step in whichexposure is performed on the entire surface again before baking isperformed and after exposing to light and developing for patterning, itis possible to make the angle smaller.

Subsequently, a light-emitting laminated body 142 is formed to cover thefirst electrode (anode) 152 exposed from the partition wall 141. Thelight-emitting laminated body 142 may be formed by a vapor depositionmethod, a spin coating method, an ink-jet method, or the like.Subsequently, a second electrode (cathode) 143 is formed to cover thelight-emitting laminated body 142 (FIG. 6C). Accordingly, alight-emitting element including the first electrode (anode) 152, thelight-emitting laminated body 142, and the second electrode (cathode)143 can be manufactured. As a cathode material for forming the secondelectrode (cathode) 143, it is preferable to use metal, an alloy, anelectrically conductive compound, each of which has low work function(work function of 3.8 eV or less), a mixture of these, or the like. Notethat as specific examples of the cathode material, the followings can begiven: an element belonging to group 1 or 2 of the periodic table suchas Li or Cs, which are alkali metal, Mg, Ca, or Sr, which arealkali-earth metal; an alloy (Mg:Ag or Al:Li) or a compound (LiF, CsF,or CaF₂) containing the above element. In addition, the cathode can alsobe formed from transition metal containing rare-earth metal. Further, amultilayer formed of the above material and metal (including an alloy)such as Al, Ag, or ITO can be used. In this Embodiment Mode, the cathodeis formed from aluminum.

Note that a buffer layer may be formed in the light-emitting element.Refer to Embodiment Mode 1 for the explanation of the buffer layer.

Note that in this Embodiment Mode, the anode is electrically in contactwith the conductive film 159 as the drain electrode of the driving TFTfor the light-emitting element. Alternatively, the cathode may beelectrically in contact with the conductive film 159.

Thereafter, a silicon nitride film containing oxygen may be formed as apassivation film by a plasma CVD method. In the case of using thesilicon nitride film containing oxygen, a silicon nitride filmcontaining oxygen formed from SiH₄, N₂O, and NH₃, a silicon nitride filmcontaining oxygen formed from SiH₄ and N₂O, or a silicon nitride filmcontaining oxygen formed from a gas in which SiH₄ and N₂O are dilutedwith Ar may be deposited by a plasma CVD method.

Alternatively, a silicon oxynitride hydride film formed from SiH₄, N₂O,and H₂ may be used as the passivation film. Naturally, a structure ofthe passivation film is not limited to a single layer structure. Thepassivation film may have a single layer structure or a laminatedstructure of another insulating film containing silicon. In addition, amultilayer film of a carbon nitride film and a silicon nitride film, amultilayer film of styrene polymer, a silicon nitride film, or a diamondlike carbon film may be formed as a substitute for a silicon nitridefilm containing oxygen.

The passivation film can suppress the entrance of elements which promotedeterioration of a light-emitting element from the top surface of thelight-emitting element; thus the reliability is improved.

Subsequently, in order to protect the light-emitting element from adeterioration-promoting material such as water, the display portion issealed (FIG. 6D). In the case of using an opposite substrate 145 forsealing, the opposite substrate is attached by an insulating sealingmaterial 144. The space between the opposite substrate 145 and theelement substrate may be filled with inert gas such as dry nitrogen;alternatively, the sealing material may be applied to the entire surfaceof the pixel portion for attaching the opposite substrate 145. It ispreferable to use an ultraviolet curable resin or the like as thesealing material 144. A drying agent or particles for keeping the gapbetween the substrates uniform may be mixed into the sealing material144.

Further, the method for manufacturing a display device of the inventionis applied to a light-emitting device including a thin film transistorof another shape; the example is shown in FIG. 21B. The differencebetween FIG. 21B and FIG. 6D is the structures of the gate insulatingfilms and shapes of the gate electrodes. In FIG. 21B, a gate insulatingfilm is formed of two layers: a first gate insulating film 400 and asecond gate insulating film 401. In addition, a gate electrode 402 has asingle layer structure having a tapered shape in its edge portion. Thefirst gate insulating film 400 is preferably formed of a siliconoxide-based film having a high insulating property and few trap levelssince it is in contact with a semiconductor layer. In addition, formingthe second gate insulating film 401 with a silicon nitride-based filmcan make the operation stable even if the gate electrode 402 is formedfrom a material that is comparatively easy to be oxidized such as Mo. Inaddition, a sealing material 144 is overlapped with an interlayerinsulating film 129.

A light-emitting device thus manufactured has few defects caused byunevenness under a light-emitting element. Further, water does notpenetrate from external atmosphere through a planarizing film;therefore, the light-emitting device has high reliability.

Furthermore, an example of a liquid crystal display device manufacturedwith the method for manufacturing a display device of the invention isshown in FIG. 22B. After the liquid crystal display device ismanufactured up to the state shown in FIG. 6A, a spacer 301 is obtainedby forming an insulating film and patterning it. Thereafter, analignment film 302 is formed over the entire surface, and then rubbingtreatment is performed.

Subsequently, a sealing material 144 is formed by a droplet dischargemethod or the like, and then liquid crystal 300 is dropped and sealed inby an opposite substrate 306. A method for sealing in liquid crystal isdescribed below. A pattern of the sealing material 144 is made a closedpattern, and liquid crystal may be dropped by a liquid crystal droppingapparatus. Alternatively, an opening is formed in the pattern of thesealing material 144, and the opposite substrate 306 is attached;thereafter, a dip method (pumping up method) using a capillaryphenomenon may be employed. In addition, the sealing material 144 isoverlapped with an interlayer insulating film 129.

The opposite substrate 306 is provided with an opposite electrode 304and an alignment film 303 in advance.

The spacer 301 is formed by patterning the insulating film in FIG. 22B;however, a spherical spacer prepared separately may be dispersed overthe alignment film 302 in order to control a cell gap.

As described above, a liquid crystal display device can be completed byapplying the method for manufacturing a display device of the invention.

Embodiment Mode 3

A method for manufacturing a display device of the present invention,which is different from those of Embodiment Modes 1 and 2, will bedescribed with reference to FIGS. 7 and 8. The processing steps arehalfway the same as those of Embodiment Mode 1; thus, the descriptionand diagrams are omitted. Refer to Embodiment Mode 1. FIG. 7Acorresponds to FIG. 2B.

After manufacturing up to the state shown in FIG. 7A followingEmbodiment Mode 1, a planarizing film 150 is formed to cover aninterlayer insulating film 129 (FIG. 7B). As a material of theplanarizing film 150, an application film with a self-planarizingproperty that can relieve unevenness formed in the lower layer byforming the film, for example, acrylic, polyimide, or siloxane ispreferably used. That is, a material that can form a film havingunevenness smaller than that formed in the lower layer can be publiclyemployed. In addition, a film of which unevenness is relieved byreflowing or polishing the film once formed may be used. In thisEmbodiment Mode, the planarizing film 150 is formed from siloxane. Thisinsulating film having a self-planarizing property such as siloxane isapplied; thus, it is possible to relieve unevenness due to a reflectionof ridges of semiconductor layers 103 and 104 or a slight unevenness ofthe interlayer insulating film, and to perform planarization.

Subsequently, a conductive film having a light transmitting property isformed to cover the planarizing film 150, and then a first electrode(anode) 152 of a thin film light-emitting element is formed byprocessing the conductive film having a light transmitting property withthe use of a mask 151 of resist or the like (FIG. 7C). A material of thefirst electrode (anode) 152 is the same as that of Embodiment Mode 1;thus, the description is omitted. Refer to Embodiment Mode 1. In thisEmbodiment Mode, ITO is used as the first electrode (anode) 152.

Next, contact holes reaching to the semiconductor layers 103 and 104 areopened (FIG. 7D). The contact holes can be formed by etching with theuse of a mask 170 of resist or the like until the semiconductor layers103 and 104 are exposed. Either wet etching or dry etching can beemployed. Note that, etching may be performed once or in several batchesdepending on a condition. When etching is carried out in severalbatches, both wet etching and dry etching may be employed.

Next, a conductive film is formed to cover the contact holes and theinterlayer insulating film. The conductive film is processed into apredetermined shape using a mask 171 of resist or the like in order toform conductive films 172 to 176 to be a wiring and source or drainelectrodes (FIG. 7E). This conductive film may be a single layer of asingle metal such as aluminum or copper, a metal alloy typified by analuminum alloy such as an alloy of aluminum, carbon and titanium, analloy of aluminum, carbon and nickel, or an alloy of aluminum, carbonand titanium, a compound, or the like. However, in this Embodiment Mode,this conductive film is a laminated structure of molybdenum, aluminumand molybdenum in this order of manufacture. In addition, a laminatedstructure formed of titanium, aluminum and titanium; titanium, titaniumnitride, aluminum and titanium; titanium and an aluminum alloy, or thelike may be employed. In addition, a conductive film 176 to be the drainelectrode of the driving TFT for the pixel portion is electrically incontact with the first electrode (anode) 152 that is a pixel electrode.

Subsequently, the planarizing film 150 is removed by etching with theuse of the conductive films 172 to 176 and the first electrode (anode)152 as masks (FIG. 7E). This removing of the planarizing film 150 may beperformed at the same time as the etching performed in manufacturing theconductive films 172 to 176; alternatively, it may be performedseparately. By removing the planarizing film 150 in this processingstep, the planarizing film 150 corresponding to the first electrode(anode) 152 remains; thus, planarization is realized under the firstelectrode (anode) 152, which is a portion in which the light-emittingelement is formed; on the other hand, the planarizing film 150corresponding to the other portion is removed. Therefore, theplanarizing film is not exposed outside a sealant forming region, andthe planarizing film 150 is not exposed to external atmosphere.Consequently, penetration of water into the inside of a panel throughthe planarizing film 150 is prevented, and it is possible to decreasedeterioration of the light-emitting element due to water.

In addition, the planarizing film 150 remains under the first electrode(anode) 152 of the light-emitting element; thus, planarization isrealized, and a defect caused by unevenness under the light-emittingelement can be decreased. Note that it is desirable that unevenness ofthe first electrode of the light-emitting element is 30 nm or less in aP−V value of one pixel, preferably 15 nm or less, more preferably 10 nmor less. When the unevenness of the first electrode belongs to the aboverange in the P−V value of one pixel, an increasing type defect can begreatly decreased.

In this processing step, a new special mask is not required; theconductive films 172 to 176, the first electrode (anode) 152 and themask 171 of resist or the like used in manufacturing the above are used.Therefore, it is unnecessary to further increase a processing step suchas photolithography, and planarization of the anode is realized withoutincreasing processing steps considerably.

A light-emitting device manufactured with the thus formed elementsubstrate in which the first electrode (anode) 152 is used as a firstelectrode of a light-emitting element has few defects caused byunevenness under the light-emitting element. Further, since water doesnot penetrate from external atmosphere through a planarizing film, thereliability is high. Hereinafter, an example of a manufacturing methodof a light-emitting element and a display device using the firstelectrode (anode) 152 fabricated by following this Embodiment Mode isshown. Needless to say, the manufacturing method of a light-emittingelement and a display device is not limited to this.

An insulating film is formed of an organic or inorganic material tocover the interlayer insulating film 129 and the first electrode (anode)152. Subsequently, the insulating film is processed to expose part ofthe first electrode (anode) 152, thereby forming a partition wall 141(FIG. 8A). As a material of the partition wall 141, a photosensitiveorganic material (acrylic, polyimide, or the like) is preferably used;however, a non-photosensitive organic material or an inorganic materialmay also be used. Further, the partition wall 141 may be used as a blackmatrix by making the partition wall 141 black in such a way that a blackpigment or dye such as titanium black or carbon nitride is diffused intothe material of the partition wall 141 with the use of a diffusematerial or the like. It is desirable that the partition wall 141 has atapered shape in its end surface toward the first electrode (anode) 152with its curvature changing continuously.

Note that it is desirable that an angle formed by the end surface of thepartition wall 141 toward the first electrode 152 side and the firstelectrode 152 is approximately 45±5°. Photosensitive polyimide is usedas the material of the partition wall 141 in order to obtain such ashape; specifically, the film thickness is approximately 1.0 μm, thetemperature of baking performed after exposing to light and developingfor patterning is approximately 300° C., thereby obtaining a preferableangle of approximately 43°. In addition, if a processing step in whichexposure is performed on the entire surface again before baking isperformed and after exposing to light and developing for patterning, itis possible to make the angle smaller.

Subsequently, a light-emitting laminated body 142 is formed to cover thefirst electrode (anode) 152 exposed from the partition wall 141. Thelight-emitting laminated body 142 may be formed by a vapor depositionmethod, a spin coating method, an ink-jet method, or the like.Subsequently, a second electrode (cathode) 143 is formed to cover thelight-emitting laminated body 142 (FIG. 8B). Accordingly, alight-emitting element including the first electrode (anode) 152, thelight-emitting laminated body 142, and the second electrode (cathode)143 can be manufactured. As a cathode material for forming the secondelectrode (cathode) 143, it is preferable to use metal, an alloy, anelectrically conductive compound, each of which has low work function(work function of 3.8 eV or less), a mixture of these, or the like. Notethat as specific examples of the cathode material, the followings can begiven: an element belonging to group 1 or 2 of the periodic table suchas Li or Cs, which are alkali metal, Mg, Ca, or Sr, which arealkali-earth metal; an alloy (Mg:Ag or Al:Li) or a compound (LiF, CsF,or CaF₂) containing the above element. In addition, the cathode can alsobe formed from transition metal containing rare-earth metal. Further, amultilayer formed of the above material and metal (including an alloy)such as Al, Ag, or ITO can be used. In this Embodiment Mode, the cathodeis formed from aluminum.

Note that a buffer layer may be formed in the light-emitting element.Refer to Embodiment Mode 1 for the explanation of the buffer layer.

Note that in this Embodiment Mode, the anode is electrically in contactwith the conductive film 176 as the drain electrode of the driving TFTfor the light-emitting element. Alternatively, the cathode may beelectrically in contact with the conductive film 176.

Thereafter, a silicon oxide film containing nitrogen may be formed as apassivation film by a plasma CVD method. In the case of using thesilicon oxide film containing nitrogen, a silicon oxynitride film formedfrom SiH₄, N₂O, and NH₃, a silicon oxynitride film formed from SiH₄ andN₂O, or a silicon oxynitride film formed from a gas in which SiH₄ andN₂O are diluted with Ar may be deposited by a plasma CVD method.

Alternatively, a silicon oxynitride hydride film formed from SiH₄, N₂O,and H₂ may be used as the passivation film. Naturally, a structure ofthe passivation film is not limited to a single layer structure. Thepassivation film may have a single layer structure or a laminatedstructure of another insulating film containing silicon. In addition, amultilayer film of a carbon nitride film and a silicon nitride film, amultilayer film of styrene polymer, a silicon nitride film, or a diamondlike carbon film may be formed as a substitute for a silicon oxide filmcontaining nitrogen.

The passivation film can suppress the entrance of elements which promotedeterioration of a light-emitting element from the top surface of thelight-emitting element; thus the reliability is improved.

Subsequently, in order to protect the light-emitting element from adeterioration-promoting material such as water, the display portion issealed (FIG. 8C). In the case of using an opposite substrate 145 forsealing, the opposite substrate is attached by an insulating sealingmaterial 144. In this Embodiment Mode, since the planarizing film 150remains under the conductive film 172 to be the wiring, it is preferablethat the sealing material 144 is provided so as not to be overlappedwith the conductive film 172 in a lead portion. By thus providing thesealing material, penetration of water through the sealing material 144and the planarizing film 150 under the conductive film 172 can beeffectively prevented.

The space between the opposite substrate 145 and the element substratemay be filled with inert gas such as dry nitrogen; alternatively, thesealing material may be applied to the entire surface of the pixelportion for attaching the opposite substrate 145. It is preferable touse an ultraviolet curable resin or the like as the sealing material144. A drying agent or particles for keeping the gap between thesubstrates uniform may be mixed into the sealing material 144.

A light-emitting device thus manufactured has few defects caused byunevenness under a light-emitting element. Further, water does notpenetrate from external atmosphere through a planarizing film;therefore, the light-emitting device has high reliability.

Further, the method for manufacturing a display device of the inventionis applied to a light-emitting device including a thin film transistorof another shape; the example is shown in FIG. 21C. The differencebetween FIG. 21C and FIG. 8C is the structures of the gate insulatingfilms and shapes of the gate electrodes. In FIG. 21C, a gate insulatingfilm is formed of two layers: a first gate insulating film 400 and asecond gate insulating film 401. In addition, a gate electrode 402 has asingle layer structure having a tapered shape in its edge portion. Thefirst gate insulating film 400 is preferably formed of a siliconoxide-based film having a high insulating property and few trap levelssince it is in contact with a semiconductor layer. In addition, formingthe second gate insulating film 401 with a silicon nitride-based filmcan make the operation stable even if the gate electrode 402 is formedfrom a material that is comparatively easy to be oxidized such as Mo. Inaddition, a sealing material 144 is overlapped with an interlayerinsulating film 129.

Furthermore, an example of a liquid crystal display device manufacturedwith the method for manufacturing a display device of the invention isshown in FIG. 22C. After the liquid crystal display device ismanufactured up to the state shown in FIG. 7E, a spacer 301 is obtainedby forming an insulating film and patterning it. Thereafter, analignment film 302 is formed over the entire surface, and then rubbingtreatment is performed.

Subsequently, a sealing material 144 is formed by a droplet dischargemethod or the like, and then liquid crystal 300 is dropped and sealed inby an opposite substrate 306. A method for sealing in liquid crystal isdescribed below. A pattern of the sealing material 144 is made a closedpattern, and liquid crystal may be dropped by a liquid crystal droppingapparatus. Alternatively, an opening is formed in the pattern of thesealing material 144, and the opposite substrate 306 is attached;thereafter, a dip method (pumping up method) using a capillaryphenomenon may be employed. In addition, the sealing material 144 isoverlapped with an interlayer insulating film 129.

The opposite substrate 306 is provided with an opposite electrode 304and an alignment film 303 in this order from the opposite substrate 306side in advance.

The spacer 301 is formed by patterning the insulating film in FIG. 22C;however, a spherical spacer prepared separately may be dispersed overthe alignment film 302 in order to control a cell gap.

As described above, a liquid crystal display device can be completed byapplying the method for manufacturing a display device of the invention.

Embodiment Mode 4

A method for manufacturing a display device, which is different fromthose of Embodiment Modes 1 to 3, will be described with reference toFIGS. 9 and 10. The processing steps are halfway the same as those ofEmbodiment Mode 1; thus, the description and diagrams are omitted. Referto Embodiment Mode 1. FIG. 9A corresponds to FIG. 2B.

After manufacturing up to the state shown in FIG. 9A followingEmbodiment Mode 1, an extremely thin planarizing film 190 is formed tocover an interlayer insulating film 129 to the extent that unevenness ofthe interlayer insulating film 129 is hidden (FIG. 9B). As a material ofthe planarizing film 190, an application film with a self-planarizingproperty that can relieve unevenness formed in the lower layer byforming the film, for example, acrylic, polyimide, or siloxane ispreferably used. That is, a material that can form a film havingunevenness smaller than that formed in the lower layer can be publiclyemployed. In addition, a film of which unevenness is relieved byreflowing or polishing the film once formed may be used. In thisEmbodiment Mode, the planarizing film 190 is formed from siloxane. Thisinsulating film having a self-planarizing property such as siloxane isapplied; thus, it is possible to relieve unevenness due to a reflectionof ridges of semiconductor layers 103 and 104 or a slight unevenness ofthe interlayer insulating film, and to perform planarization.

Next, contact holes reaching to the semiconductor layers 103 and 104 areopened (FIG. 9C). The contact holes can be formed by etching with theuse of a mask 191 of resist or the like until the semiconductor layers103 and 104 are exposed. Either wet etching or dry etching can beemployed. Note that, etching may be performed once or in several batchesdepending on a condition. When etching is carried out in severalbatches, both wet etching and dry etching may be employed.

Next, a conductive film is formed to cover the contact holes and theinterlayer insulating film. The conductive film is processed into apredetermined shape using a mask 192 of resist or the like in order toform conductive films 193 to 197 to be a wiring and source or drainelectrodes (FIG. 9(D)). A single metal such as aluminum or copper, ametal alloy typified by an aluminum alloy such as an alloy of aluminum,carbon and titanium, an alloy of aluminum, carbon and nickel, or analloy of aluminum, carbon and titanium, a compound, or the like can beused for forming this conductive film. The conductive film may be formedof a single layer; however, in this Embodiment Mode, this conductivefilm is a laminated structure of molybdenum, aluminum and molybdenum inthis order of manufacture. In addition, a laminated structure formed oftitanium, aluminum and titanium; titanium, titanium nitride, aluminumand titanium; titanium and an aluminum alloy, or the like may beemployed.

Subsequently, a conductive film having a light transmitting property isformed to cover the interlayer insulating film 129 and the conductivefilms 193 to 197, and then a first electrode (anode) 199 of a thin filmlight-emitting element is formed by processing the conductive filmhaving a light transmitting property with the use of a mask 198 ofresist or the like by etching (FIG. 9E). Here, the first electrode(anode) 199 is electrically in contact with the conductive film 197 ofthe driving TFT for the light-emitting element. A material of the firstelectrode (anode) 199 is the same as that of Embodiment Mode 1; thus,the description is omitted. Refer to Embodiment Mode 1. In thisEmbodiment Mode, ITO is used as the first electrode (anode) 199.

A light-emitting device manufactured with the thus formed elementsubstrate in which the first electrode (anode) 199 is used as a firstelectrode of a light-emitting element has few defects caused byunevenness under the light-emitting element. Further, since water hardlypenetrates from external atmosphere through a planarizing film due tothe extremely thin planarizing film 190, the reliability is high.Hereinafter, an example of a manufacturing method of a light-emittingelement and a display device using the first electrode (anode) 199fabricated by following this Embodiment Mode is shown. Needless to say,the manufacturing method of a light-emitting element and a displaydevice is not limited to this.

Note that it is desirable that unevenness of the first electrode of thelight-emitting element is 30 nm or less in a P−V value of one pixel,preferably 15 nm or less, more preferably 10 nm or less. When theunevenness of the first electrode belongs to the above range in the P−Vvalue of one pixel, an increasing type defect can be greatly decreased.

An insulating film is formed of an organic or inorganic material tocover the interlayer insulating film 129 and the first electrode (anode)199. Subsequently, the insulating film is processed to expose part ofthe first electrode (anode) 199, thereby forming a partition wall 141(FIG. 10A). As a material of the partition wall 141, a photosensitiveorganic material (acrylic, polyimide, or the like) is preferably used;however, a non-photosensitive organic material or an inorganic materialmay also be used. Further, the partition wall 141 may be used as a blackmatrix by making the partition wall 141 black in such a way that a blackpigment or dye such as titanium black or carbon nitride is diffused intothe material of the partition wall 141 with the use of a diffusematerial or the like. It is desirable that the partition wall 141 has atapered shape in its end surface toward the first electrode (anode) 199with its curvature changing continuously.

Note that it is desirable that an angle formed by the end surface of thepartition wall 141 toward the first electrode 199 side and the firstelectrode 199 is approximately 45±5°. Photosensitive polyimide is usedas the material of the partition wall 141 in order to obtain such ashape; specifically, the film thickness is approximately 1.0 μm, thetemperature of baking performed after exposing to light and developingfor patterning is approximately 300° C., thereby obtaining a preferableangle of approximately 43°. In addition, if a processing step in whichexposure is performed on the entire surface again before baking isperformed and after exposing to light and developing for patterning, itis possible to make the angle smaller.

Subsequently, a light-emitting laminated body 142 is formed to cover thefirst electrode (anode) 199 exposed from the partition wall 141. Thelight-emitting laminated body 142 may be formed by a vapor depositionmethod, a spin coating method, an ink-jet method, or the like.Subsequently, a second electrode (cathode) 143 is formed to cover thelight-emitting laminated body 142 (FIG. 10B). Accordingly, alight-emitting element including the first electrode (anode) 199, thelight-emitting laminated body 142, and the second electrode (cathode)143 can be manufactured. As a cathode material for forming the secondelectrode (cathode) 143, it is preferable to use metal, an alloy, anelectrically conductive compound, each of which has low work function(work function of 3.8 eV or less), a mixture of these, or the like. Notethat as specific examples of the cathode material, the following can begiven: an element belonging to group 1 or 2 of the periodic table suchas Li or Cs, which are alkali metal, Mg, Ca, or Sr, which arealkali-earth metal; an alloy (Mg:Ag or Al:Li) or a compound (LiF, CsF,or CaF₂) containing the above element. In addition, the cathode can alsobe formed from transition metal containing rare-earth metal. Further, amultilayer formed of the above material and metal (including an alloy)such as Al, Ag, or ITO can be used. In this Embodiment Mode, the cathodeis formed from aluminum.

Note that a buffer layer may be formed in the light-emitting element.Refer to Embodiment Mode 1 for the explanation of the buffer layer.

Note that in this Embodiment Mode, the anode is electrically in contactwith the conductive film 197 of the driving TFT for the light-emittingelement. Alternatively, the cathode may be electrically in contact withthe conductive film 197.

Thereafter, a silicon nitride film containing oxygen may be formed as apassivation film by a plasma CVD method. In the case of using thesilicon nitride film containing oxygen, a silicon nitride filmcontaining oxygen formed from SiH₄, N₂O, and NH₃, a silicon nitride filmcontaining oxygen formed from SiH₄ and N₂O, or a silicon nitride filmcontaining oxygen formed from a gas in which SiH₄ and N₂O are dilutedwith Ar may be deposited by a plasma CVD method.

Alternatively, a silicon nitride film containing hydrogen and oxygenformed from SiH₄, N₂O, and H₂ may be used as the passivation film.Naturally, a structure of the passivation film is not limited to asingle layer structure. The passivation film may have a single layerstructure or a laminated structure of another insulating film containingsilicon. In addition, a multilayer film of a carbon nitride film and asilicon nitride film, a multilayer film of styrene polymer, a siliconnitride film, or a diamond like carbon film may be formed as asubstitute for a silicon nitride film containing oxygen.

The passivation film can suppress the entrance of elements which promotedeterioration of a light-emitting element from the top surface of thelight-emitting element; thus the reliability is improved.

Subsequently, in order to protect the light-emitting element from adeterioration-promoting material such as water, the display portion issealed (FIG. 10C). In the case of using an opposite substrate 145 forsealing, the opposite substrate is attached by an insulating sealingmaterial 144. In this Embodiment Mode, since the planarizing film 190remains under the conductive film 193 to be the wiring, it is preferablethat the sealing material 144 is provided so as not to be overlappedwith the conductive film 193 in a lead portion. By thus providing thesealing material, penetration of water through the sealing material 144and the planarizing film 190 under the conductive film 193 can beeffectively prevented.

The space between the opposite substrate 145 and the element substratemay be filled with inert gas such as dry nitrogen; alternatively, thesealing material may be applied to the entire surface of a pixel portionfor attaching the opposite substrate 145. It is preferable to use anultraviolet curable resin or the like as the sealing material 144. Adrying agent or particles for keeping the gap between the substratesuniform may be mixed into the sealing material 144.

A light-emitting device thus manufactured has few defects caused byunevenness under a light-emitting element. Further, water does notpenetrate from external atmosphere through a planarizing film;therefore, the light-emitting device has high reliability.

Further, the method for manufacturing a display device of the inventionis applied to a light-emitting device including a thin film transistorof another shape; the example is shown in FIG. 21D. The differencebetween FIG. 21D and FIG. 10C is the structures of the gate insulatingfilms and shapes of the gate electrodes. In FIG. 21D, a gate insulatingfilm is formed of two layers: a first gate insulating film 400 and asecond gate insulating film 401. In addition, a gate electrode 402 has asingle layer structure having a tapered shape in its edge portion. Thefirst gate insulating film 400 is preferably formed of a siliconoxide-based film having a high insulating property and few trap levelssince it is in contact with a semiconductor layer. In addition, formingthe second gate insulating film 401 with a silicon nitride-based filmcan make the operation stable even if the gate electrode 402 is formedfrom a material that is comparatively easy to be oxidized such as Mo. Inaddition, a sealing material 144 is overlapped with an interlayerinsulating film 129.

Furthermore, an example of a liquid crystal display device manufacturedwith the method for manufacturing a display device of the invention isshown in FIG. 22D. After the liquid crystal display device ismanufactured up to the state shown in FIG. 9E, a spacer 301 is obtainedby forming an insulating film and patterning it. Thereafter, analignment film 302 is formed over the entire surface of the exposedportion, and then rubbing treatment is performed.

Subsequently, a sealing material 144 is formed by a droplet dischargemethod or the like, and then liquid crystal 300 is dropped and sealed inby an opposite substrate 306. A method for sealing in liquid crystal isdescribed below. A pattern of the sealing material 144 is made a closedpattern, and liquid crystal may be dropped by a liquid crystal droppingapparatus. Alternatively, an opening is formed in the pattern of thesealing material 144, and the opposite substrate 306 is attached;thereafter, a dip method (pumping up method) using a capillaryphenomenon may be employed. In addition, the sealing material 144 isoverlapped with an interlayer insulating film 129.

The opposite substrate 306 is provided with an opposite electrode 304and an alignment film 303 in this order from the opposite substrate 306side in advance.

The spacer 301 is formed by patterning the insulating film in FIG. 22A;however, a spherical spacer prepared separately may be dispersed overthe alignment film 302 in order to control a cell gap.

As described above, a liquid crystal display device can be completed byapplying the method for manufacturing a display device of the invention.

Embodiment Mode 5

A method for manufacturing a display device of the present invention,which is different from those of Embodiment Modes 1 to 4, will bedescribed with reference to FIGS. 11 and 12. The processing steps arehalfway the same as those of Embodiment Mode 1; thus, the descriptionand diagrams are omitted. Refer to Embodiment Mode 1. FIG. 11Acorresponds to FIG. 3A.

After manufacturing up to the state shown in FIG. 11A, a secondinterlayer insulating film 200 is formed to cover a planarizing film 137and an exposed portion of a conductive film 136. As a material forforming the second interlayer insulating film 200, an inorganicinsulating film such as silicon oxide, silicon nitride, or a Low-kmaterial may be used. In this Embodiment Mode, a silicon oxide film isformed as the second interlayer insulating film.

Next, a contact hole reaching to the conductive film 136 is opened inthe second interlayer insulating film 200. The contact hole can beformed by etching with the use of a mask 201 of resist or the like untila source electrode or the conductive film 136 is exposed. Either wetetching or dry etching can be employed.

After forming the contact hole, the planarizing film 137 is removed byetching with the use of the mask 201 as a mask without removing the mask201 of resist or the like (FIG. 11C).

Subsequently, a conductive film having a light transmitting property isformed to cover the exposed portion of the conductive film 136, and thena first electrode (anode) 203 of a thin film light-emitting element isformed by processing the conductive film having a light transmittingproperty with the use of a mask 202 of resist or the like by etching(FIG. 11D). Here, the first electrode (anode) 203 is electrically incontact with the conductive film 136 of the driving TFT for thelight-emitting element. As a material of the first electrode (anode)203, metal, an alloy, an electrically conductive compound each of whichhas high work function (work function of 4.0 eV or more), a mixture ofthese, or the like is preferably used. For example, ITO (indium tinoxide), ITO containing silicon (ITSO), IZO (indium zinc oxide) in whichzinc oxide (ZnO) is mixed by 2 to 20 atomic % into indium oxide, zincoxide, GZO (gallium zinc oxide) in which gallium is mixed into zincoxide, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium(Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium(Pd), or metal nitride (TiN) can be used. In this Embodiment Mode, ITSOis used as the first electrode (anode) 203.

By removing the planarizing film 137 in this processing step, theplanarizing film 137 corresponding to the first electrode (anode) 203remains; thus, planarization is realized under the first electrode(anode) 203, which is a portion in which the light-emitting element isformed; on the other hand, the planarizing film 137 around the substrate100 is removed. Therefore, the planarizing film is not exposed outside asealant forming region, and the planarizing film 137 is not exposed toexternal atmosphere. Consequently, penetration of water into the insideof a panel through the planarizing film 137 is prevented, and it ispossible to decrease deterioration of the light-emitting element due towater. In addition, the planarizing film 137 remains under the firstelectrode (anode) 203; thus, planarization is realized, and a defectcaused by unevenness under the light-emitting element can be decreased.Note that it is desirable that unevenness of the first electrode of thelight-emitting element is 30 nm or less in a P−V value of one pixel,preferably 15 nm or less, more preferably 10 nm or less. When theunevenness of the first electrode belongs to the above range in the P−Vvalue of one pixel, an increasing type defect can be greatly decreased.

Note that in this processing step of removing the planarizing film 137,a new special mask is not required; the mask 201 of resist or the likeused in forming the contact hole in the second interlayer insulatingfilm 200 is used. Therefore, it is unnecessary to further increase aprocessing step such as photolithography, and planarization of the anodeis realized without increasing processing steps considerably.

A light-emitting device manufactured with the thus formed elementsubstrate in which the first electrode (anode) 203 is used as a firstelectrode of a light-emitting element has few defects caused byunevenness under the light-emitting element. Further, since water doesnot penetrate from external atmosphere through a planarizing film, thereliability is high. Hereinafter, an example of a manufacturing methodof a light-emitting element and a display device using the firstelectrode (anode) 203 fabricated by following this Embodiment Mode isshown. Needless to say, the manufacturing method of a light-emittingelement and a display device is not limited to this.

An insulating film is formed of an organic or inorganic material tocover the second interlayer insulating film 200 and the first electrode(anode) 203. Subsequently, the insulating film is processed to exposepart of the first electrode (anode) 203, thereby forming a partitionwall 141 (FIG. 12A). As a material of the partition wall 141, aphotosensitive organic material (acrylic, polyimide, or the like) ispreferably used; however, a non-photosensitive organic material or aninorganic material may also be used. Further, the partition wall 141 maybe used as a black matrix by making the partition wall 141 black in sucha way that a black pigment or dye such as titanium black or carbonnitride is diffused into the material of the partition wall 141 with theuse of a diffuse material or the like. It is desirable that thepartition wall 141 has a tapered shape in its end surface toward thefirst electrode (anode) 203 with its curvature changing continuously.

Note that it is desirable that an angle formed by the end surface of thepartition wall 141 toward the first electrode 203 side and the firstelectrode 203 is approximately 45±5°. Photosensitive polyimide is usedas the material of the partition wall 141 in order to obtain such ashape; specifically, the film thickness is approximately 1.0 μm, thetemperature of baking performed after exposing to light and developingfor patterning is approximately 300° C., thereby obtaining a preferableangle of approximately 43°. In addition, if a processing step in whichexposure is performed on the entire surface again before baking isperformed and after exposing to light and developing for patterning isadded, it is possible to make the angle smaller.

Subsequently, a light-emitting laminated body 142 is formed to cover thefirst electrode (anode) 203 exposed from the partition wall 141. Thelight-emitting laminated body 142 may be formed by a vapor depositionmethod, a spin coating method, an ink-jet method, or the like.Subsequently, a second electrode (cathode) 143 is formed to cover thelight-emitting laminated body 142 (FIG. 12B). Accordingly, alight-emitting element including the first electrode (anode) 203, thelight-emitting laminated body 142, and the second electrode (cathode)143 can be manufactured. As a cathode material for forming the secondelectrode (cathode) 143, it is preferable to use metal, an alloy, anelectrically conductive compound, each of which has low work function(work function of 3.8 eV or less), a mixture of these, or the like. Notethat as specific examples of the cathode material, the following can begiven: an element belonging to group 1 or 2 of the periodic table suchas Li or Cs, which are alkali metal, Mg, Ca, or Sr, which arealkali-earth metal; an alloy (Mg:Ag or Al:Li) or a compound (LiF, CsF,or CaF₂) containing the above element. In addition, the cathode can alsobe formed from transition metal containing rare-earth metal. Further, amultilayer formed of the above material and metal (including an alloy)such as Al, Ag, or ITO can be used. In this Embodiment Mode, the cathodeis formed from aluminum.

Note that a buffer layer may be formed in the light-emitting element.Refer to Embodiment Mode 1 for the explanation of the buffer layer.

Note that in this Embodiment Mode, the anode is electrically in contactwith the conductive film 136 of the driving TFT for the light-emittingelement. Alternatively, the cathode may be electrically in contact withthe conductive film 136.

Thereafter, a silicon nitride film containing oxygen may be formed as apassivation film by a plasma CVD method. In the case of using thesilicon nitride film containing oxygen, a silicon nitride filmcontaining oxygen formed from SiH₄, N₂O, and NH₃, a silicon nitride filmcontaining oxygen formed from SiH₄ and N₂O, or a silicon nitride filmcontaining oxygen formed from a gas in which SiH₄ and N₂O are dilutedwith Ar may be deposited by a plasma CVD method.

Alternatively, a silicon nitride film containing hydrogen and oxygenformed from SiH₄, N₂O, and H₂ may be used as the passivation film.Naturally, a structure of the passivation film is not limited to asingle layer structure. The passivation film may have a single layerstructure or a laminated structure of another insulating film containingsilicon. In addition, a multilayer film of a carbon nitride film and asilicon nitride film, a multilayer film of styrene polymer, a siliconnitride film, or a diamond like carbon film may be formed as asubstitute for a silicon nitride film containing oxygen.

The passivation film can suppress the entrance of elements which promotedeterioration of a light-emitting element from the top surface of thelight-emitting element; thus the reliability is improved.

Subsequently, in order to protect the light-emitting element from adeterioration-promoting material such as water, the display portion issealed (FIG. 12C). In the case of using an opposite substrate 145 forsealing, the opposite substrate is attached by an insulating sealingmaterial 144. The space between the opposite substrate 145 and theelement substrate may be filled with inert gas such as dry nitrogen;alternatively, the sealing material may be applied to the entire surfaceof the pixel portion for attaching the opposite substrate 145. It ispreferable to use an ultraviolet curable resin or the like as thesealing material 144. A drying agent or particles for keeping the gapbetween the substrates uniform may be mixed into the sealing material144.

A light-emitting device thus manufactured has few defects caused byunevenness under a light-emitting element. Further, a planarizing filmis not in contact with external atmosphere, and water does not penetratethrough the planarizing film; therefore, the light-emitting device hashigh reliability.

Embodiment Mode 6

A method for manufacturing a display device of the present invention,which is different from those of Embodiment Modes 1 to 5, will bedescribed with reference to FIGS. 13 and 14. The processing steps arehalfway the same as those of Embodiment Mode 1; thus, the descriptionand diagrams are omitted. Refer to Embodiment Mode 1. FIG. 13Acorresponds to FIG. 2D.

After manufacturing up to the state shown in FIG. 13A, a secondinterlayer insulating film 210 is formed to cover conductive films 132to 136 and an interlayer insulating film 129 after removing a mask 131.As a material for forming the second interlayer insulating film 210, aninorganic insulating film such as silicon oxide, silicon nitride, or aLow-k material may be used. In this Embodiment Mode, a silicon oxidefilm is formed as the second interlayer insulating film 210.

Next, a contact hole reaching to the conductive film 136 is opened inthe second interlayer insulating film 210 (FIG. 13B). The contact holecan be formed by etching with the use of a mask 211 of resist or thelike until the conductive film 136 is exposed. Either wet etching or dryetching can be employed.

Next, the mask 211 is removed, and then a conductive film is formed tocover the contact hole and the second interlayer insulating film 210.The conductive film is processed into a predetermined shape using a maskof resist or the like in order to form a wiring 212 electricallyconnected to the conductive film 136. A single metal such as aluminum orcopper, a metal alloy typified by an aluminum alloy such as an alloy ofaluminum, carbon and titanium, an alloy of aluminum, carbon and nickel,or an alloy of aluminum, carbon and titanium, a compound, or the likemay be used for forming this conductive film. The conductive film may beformed of a single layer; however, in this Embodiment Mode, thisconductive film is a laminated structure of molybdenum, aluminum andmolybdenum in this order of manufacture. In addition, a laminatedstructure formed of titanium, aluminum and titanium; titanium, titaniumnitride, aluminum and titanium; titanium and an aluminum alloy, or thelike may be employed.

Subsequently, a planarizing film 213 is formed to cover the secondinterlayer insulating film 210 and the wiring 212 (FIG. 13C). As amaterial of the planarizing film 213, an application film with aself-planarizing property that can relieve unevenness formed in thelower layer by forming the film, for example, acrylic, polyimide, orsiloxane is preferably used. That is, a material that can form a filmhaving unevenness smaller than that formed in the lower layer can bepublicly employed. In addition, a film of which unevenness is relievedby reflowing or polishing the film once formed may be used. In thisEmbodiment Mode, the planarizing film 213 is formed from siloxane. Thisinsulating film having a self-planarizing property such as siloxane isapplied; thus, it is possible to relieve unevenness due to a reflectionof ridges of semiconductor layers 103 and 104, a slight unevenness ofthe interlayer insulating film, and unevenness of the lower layergenerated such as in forming the conductive films 132 to 136 and thewiring 212, and to perform planarization.

Subsequently, a conductive film having a light transmitting property isformed to cover at least part of the wiring 212, and then a firstelectrode (anode) 215 of a thin film light-emitting element is formed byprocessing the conductive film having a light transmitting property withthe use of a mask 214 of resist or the like. Here, the first electrode(anode) 215 is electrically in contact with the conductive film 136 ofthe driving TFT for the light-emitting element through the wiring 212.As a material of the first electrode (anode) 215, metal, an alloy, anelectrically conductive compound each of which has high work function(work function of 4.0 eV or more), a mixture of these, or the like ispreferably used. For example, ITO (indium tin oxide), ITO containingsilicon (ITSO), IZO (indium zinc oxide) in which zinc oxide (ZnO) ismixed by 2 to 20 atomic % into indium oxide, zinc oxide, GZO (galliumzinc oxide) in which gallium is mixed into zinc oxide, gold (Au),platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum(Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or metalnitride (TiN) can be used. In this Embodiment Mode, ITSO is used as thefirst electrode (anode) 215.

After forming the first electrode (anode) 215, the planarizing film 213is removed by etching with the use of the first electrode (anode) 215and the mask 214 as masks without removing the mask 214 of resist or thelike (FIG. 13D). By removing the planarizing film 213 in this processingstep, the planarizing film 213 corresponding to the first electrode(anode) 215 remains; thus, planarization is realized under the firstelectrode (anode) 215, which is a portion in which the light-emittingelement is formed; on the other hand, the planarizing film 213corresponding to the other portion is removed. Therefore, theplanarizing film is not exposed outside a sealant forming region, andthe planarizing film 213 is not exposed to external atmosphere.Consequently, penetration of water into the inside of a panel throughthe planarizing film 213 is prevented, and it is possible to decreasedeterioration of the light-emitting element due to water.

In addition, the planarizing film 213 remains under the first electrode(anode) 215 of the light-emitting element; thus, planarization isrealized, and a defect caused by unevenness under the light-emittingelement can be decreased. Note that it is desirable that unevenness ofthe first electrode of the light-emitting element is 30 nm or less in aP−V value of one pixel, preferably 15 nm or less, more preferably 10 nmor less. When the unevenness of the first electrode belongs to the aboverange in the P−V value of one pixel, an increasing type defect can begreatly decreased.

In this processing step, a new special mask is not required; the firstelectrode (anode) 215 and the mask 214 of resist or the like used inmanufacturing the anode are used. Therefore, it is unnecessary tofurther increase a processing step such as photolithography, andplanarization of the anode is realized without increasing processingsteps considerably.

A light-emitting device manufactured with the thus formed elementsubstrate in which the first electrode (anode) 215 is used as a firstelectrode of a light-emitting element has few defects caused byunevenness under the light-emitting element. Further, since water hardlypenetrates from external atmosphere through a planarizing film, thereliability is high. Hereinafter, an example of a manufacturing methodof a light-emitting element and a display device using the firstelectrode (anode) 215 fabricated by following this Embodiment Mode isshown. Needless to say, the manufacturing method of a light-emittingelement and a display device is not limited to this.

An insulating film is formed of an organic or inorganic material tocover the second interlayer insulating film 210 and the first electrode(anode) 215. Subsequently, the insulating film is processed to exposepart of the first electrode (anode) 215, thereby forming a partitionwall 141 (FIG. 14A). As a material of the partition wall 141, aphotosensitive organic material (acrylic, polyimide, or the like) ispreferably used; however, a non-photosensitive organic material or aninorganic material may also be used. Further, the partition wall 141 maybe used as a black matrix by making the partition wall 141 black in sucha way that a black pigment or dye such as titanium black or carbonnitride is diffused into the material of the partition wall 141 with theuse of a diffuse material or the like. It is desirable that thepartition wall 141 has a tapered shape in its end surface toward thefirst electrode (anode) 215 with its curvature changing continuously.

Note that it is desirable that an angle formed by the end surface of thepartition wall 141 toward the first electrode 215 side and the firstelectrode 215 is approximately 45±5°. Photosensitive polyimide is usedas the material of the partition wall 141 in order to obtain such ashape; specifically, the film thickness is approximately 1.0 μm, thetemperature of baking performed after exposing to light and developingfor patterning is approximately 300° C., thereby obtaining a preferableangle of approximately 43°. In addition, if a processing step in whichexposure is performed on the entire surface again before baking isperformed and after exposing to light and developing for patterning isadded, it is possible to make the angle smaller.

Subsequently, a light-emitting laminated body 142 is formed to cover thefirst electrode (anode) 215 exposed from the partition wall 141. Thelight-emitting laminated body 142 may be formed by a vapor depositionmethod, a spin coating method, an ink-jet method, or the like.Subsequently, a second electrode (cathode) 143 is formed to cover thelight-emitting laminated body 142 (FIG. 14B). Accordingly, alight-emitting element including the first electrode (anode) 215, thelight-emitting laminated body 142, and the second electrode (cathode)143 can be manufactured. As a cathode material for forming the secondelectrode (cathode) 143, it is preferable to use metal, an alloy, anelectrically conductive compound, each of which has low work function(work function of 3.8 eV or less), a mixture of these, or the like. Notethat as specific examples of the cathode material, the following can begiven: an element belonging to group 1 or 2 of the periodic table suchas Li or Cs, which are alkali metal, Mg, Ca, or Sr, which arealkali-earth metal; an alloy (Mg:Ag or Al:Li) or a compound (LiF, CsF,or CaF₂) containing the above element. In addition, the cathode can alsobe formed from transition metal containing rare-earth metal. Further, amultilayer formed of the above material and metal (including an alloy)such as Al, Ag, or ITO can be used. In this Embodiment Mode, the cathodeis formed from aluminum.

Note that a buffer layer may be formed in the light-emitting element.Refer to Embodiment Mode 1 for the explanation of the buffer layer.

Note that in this Embodiment Mode, the anode of the light-emittingelement is electrically in contact with the conductive film 136 of thedriving TFT for the light-emitting element. Alternatively, the cathodemay be electrically in contact with the conductive film 136.

Thereafter, a silicon nitride film containing oxygen may be formed as apassivation film by a plasma CVD method. In the case of using thesilicon nitride film containing oxygen, a silicon nitride filmcontaining oxygen formed from SiH₄, N₂O, and NH₃, a silicon nitride filmcontaining oxygen formed from SiH₄ and N₂O, or a silicon nitride filmcontaining oxygen formed from a gas in which SiH₄ and N₂O are dilutedwith Ar may be deposited by a plasma CVD method.

Alternatively, a silicon nitride film containing hydrogen and oxygenformed from SiH₄, N₂O, and H₂ may be used as the passivation film.Naturally, a structure of the passivation film is not limited to asingle layer structure. The passivation film may have a single layerstructure or a laminated structure of another insulating film containingsilicon. In addition, a multilayer film of a carbon nitride film and asilicon nitride film, a multilayer film of styrene polymer, a siliconnitride film, or a diamond like carbon film may be formed as asubstitute for a silicon nitride film containing oxygen.

The passivation film can suppress the entrance of elements which promotedeterioration of a light-emitting element from the top surface of thelight-emitting element; thus the reliability is improved.

Subsequently, in order to protect the light-emitting element from adeterioration-promoting material such as water, the display portion issealed (FIG. 14C). In the case of using an opposite substrate 145 forsealing, the opposite substrate is attached by an insulating sealingmaterial 144. The space between the opposite substrate 145 and theelement substrate may be filled with inert gas such as dry nitrogen;alternatively, the sealing material may be applied to the entire surfaceof the pixel portion for attaching the opposite substrate 145. It ispreferable to use an ultraviolet curable resin or the like as thesealing material 144. A drying agent or particles for keeping the gapbetween the substrates uniform may be mixed into the sealing material144.

A light-emitting device thus manufactured has few defects caused byunevenness under a light-emitting element. Further, a planarizing filmis not in contact with external atmosphere, and water does not penetratethrough the planarizing film; therefore, the light-emitting device hashigh reliability.

Embodiment Mode 7

A method for manufacturing a display device of the present invention,which is different from those of Embodiment Modes 1 to 6, will bedescribed with reference to FIGS. 15 and 16. The processing steps arehalfway the same as those of Embodiment Mode 1; thus, the descriptionand diagrams are omitted. Refer to Embodiment Mode 1. FIG. 15Acorresponds to FIG. 2D.

After manufacturing up to the state shown in FIG. 15A, a secondinterlayer insulating film 220 is formed to cover an interlayerinsulating film 129 and conductive films 132 to 136. As a material forforming the second interlayer insulating film 220, an inorganicinsulating film such as silicon oxide, silicon nitride, or a Low-kmaterial may be used. In this Embodiment Mode, a silicon oxide film isformed as the second interlayer insulating film 220.

Subsequently, a planarizing film 221 is formed to cover the secondinterlayer insulating film 220 (FIG. 15B). As a material of theplanarizing film 221, an application film with a self-planarizingproperty that can relieve unevenness formed in the lower layer byforming the film, for example, acrylic, polyimide, or siloxane ispreferably used. That is, a material that can form a film havingunevenness smaller than that formed in the lower layer can be publiclyemployed. In addition, a film of which unevenness is relieved byreflowing or polishing the film once formed may be used. In thisEmbodiment Mode, the planarizing film 221 is formed from polyimide. Thisinsulating film having a self-planarizing property such as polyimide isapplied; thus, it is possible to relieve unevenness due to a reflectionof ridges of semiconductor layers 103 and 104, a slight unevenness ofthe interlayer insulating film, and unevenness of the lower layergenerated such as in forming the conductive films 132 to 136, and toperform planarization.

Subsequently, a conductive film having a light transmitting property isformed to cover the planarizing film 221, and then a first electrode(anode) 223 of a thin film light-emitting element is formed byprocessing the conductive film having a light transmitting property withthe use of a mask 222 of resist or the like. As a material of the firstelectrode (anode) 223, metal, an alloy, an electrically conductivecompound each of which has high work function (work function of 4.0 eVor more), a mixture of these, or the like is preferably used. Forexample, ITO (indium tin oxide), ITO containing silicon (ITSO), IZO(indium zinc oxide) in which zinc oxide (ZnO) is mixed by 2 to 20 atomic% into indium oxide, zinc oxide, GZO (gallium zinc oxide) in whichgallium is mixed into zinc oxide, gold (Au), platinum (Pt), nickel (Ni),tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co),copper (Cu), palladium (Pd), or metal nitride (TiN) can be used. In thisEmbodiment Mode, ITSO is used as the first electrode (anode) 223.

After forming the first electrode (anode) 223, the planarizing film 221is removed by etching with the use of the first electrode (anode) 223and the mask 222 as masks without removing the mask 222 of resist or thelike (FIG. 15C). By removing the planarizing film 221 in this processingstep, the planarizing film 221 corresponding to the first electrode(anode) 223 remains; thus, planarization is realized under the firstelectrode (anode) 223, which is a portion in which the light-emittingelement is formed; on the other hand, the planarizing film 221corresponding to the other portion is removed. Therefore, theplanarizing film is not exposed outside a sealant forming region, andthe planarizing film 221 is not exposed to external atmosphere.Accordingly, penetration of water into the inside of a panel through theplanarizing film 221 is much decreased, and it is possible to decreasedeterioration of the light-emitting element due to water.

In addition, the planarizing film 221 remains under the first electrode(anode) 223 of the light-emitting element; thus, planarization isrealized, and a defect caused by unevenness under the light-emittingelement can be decreased. Note that it is desirable that unevenness ofthe first electrode of the light-emitting element is 30 nm or less in aP−V value of one pixel, preferably 15 nm or less, more preferably 10 nmor less. When the unevenness of the first electrode belongs to the aboverange in the P−V value of one pixel, an increasing type defect can begreatly decreased.

In this processing step, a new special mask is not required; the firstelectrode (anode) 223 and the mask 222 of resist or the like used inmanufacturing the anode are used. Therefore, it is unnecessary tofurther increase a processing step such as photolithography, andplanarization of the anode is realized without increasing processingsteps considerably.

Next, a contact hole reaching to the conductive film 136 is opened inthe second interlayer insulating film 220 (FIG. 15D). The contact holecan be formed by etching with the use of a mask 224 of resist or thelike until the conductive film 136 is exposed. Either wet etching or dryetching can be employed.

Subsequently, the mask 224 is removed, and then a conductive film isformed to cover the contact hole and the second interlayer insulatingfilm 220. The conductive film is processed into a predetermined shapeusing a mask of resist or the like in order to form such as a wiring 225formed of the conductive film electrically connected to the conductivefilm 136 and the first electrode (anode) 223 (FIG. 16A). A single metalsuch as aluminum or copper, a metal alloy typified by an aluminum alloysuch as an alloy of aluminum, carbon and titanium, an alloy of aluminum,carbon and nickel, or an alloy of aluminum, carbon and titanium, acompound, or the like may be used for forming this conductive film. Theconductive film may be formed of a single layer; however, in thisEmbodiment Mode, this conductive film is a laminated structure ofmolybdenum, aluminum and molybdenum in this order from the bottom. Inaddition, a laminated structure formed of titanium, aluminum andtitanium; titanium, titanium nitride, aluminum and titanium; titaniumand an aluminum alloy, or the like may be employed.

A light-emitting device manufactured with the thus formed elementsubstrate in which the first electrode (anode) 223 is used as a firstelectrode of a light-emitting element has few defects caused byunevenness under the light-emitting element. Further, since water doesnot penetrate from external atmosphere through a planarizing film, thereliability is high. Hereinafter, an example of a manufacturing methodof a light-emitting element and a display device using the firstelectrode (anode) 223 fabricated by following this Embodiment Mode isshown. Needless to say, the manufacturing method of a light-emittingelement and a display device is not limited to this.

An insulating film is formed of an organic or inorganic material tocover the second interlayer insulating film 220 and the first electrode(anode) 223. Subsequently, the insulating film is processed to exposepart of the first electrode (anode) 223, thereby forming a partitionwall 141 (FIG. 16B). As a material of the partition wall 141, aphotosensitive organic material (acrylic, polyimide, or the like) ispreferably used; however, a non-photosensitive organic material or aninorganic material may also be used. Further, the partition wall 141 maybe used as a black matrix by making the partition wall 141 black in sucha way that a black pigment or dye such as titanium black or carbonnitride is diffused into the material of the partition wall 141 with theuse of a diffuse material or the like. It is desirable that thepartition wall 141 has a tapered shape in its end surface toward thefirst electrode (anode) 223 with its curvature changing continuously.

Note that it is desirable that an angle formed by the end surface of thepartition wall 141 toward the first electrode 223 side and the firstelectrode 223 is approximately 45±5°. Photosensitive polyimide is usedas the material of the partition wall 141; specifically, the filmthickness is approximately 1.0 μm, the temperature of baking performedafter exposing to light and developing for patterning is approximately300° C., thereby obtaining a preferable angle of approximately 43°. Inaddition, if a processing step in which exposure is performed on theentire surface again before baking is performed and after exposing tolight and developing for patterning is added, it is possible to make theangle smaller.

Subsequently, a light-emitting laminated body 142 is formed to cover thefirst electrode (anode) 223 exposed from the partition wall 141. Thelight-emitting laminated body 142 may be formed by a vapor depositionmethod, a spin coating method, an ink-jet method, or the like.Subsequently, a second electrode (cathode) 143 is formed to cover thelight-emitting laminated body 142 (FIG. 16C). Accordingly, alight-emitting element including the first electrode (anode) 223, thelight-emitting laminated body 142, and the second electrode (cathode)143 can be manufactured. As a cathode material for forming the secondelectrode (cathode) 143, it is preferable to use metal, an alloy, anelectrically conductive compound, each of which has low work function(work function of 3.8 eV or less), a mixture of these, or the like. Notethat as specific examples of the cathode material, the following can begiven: an element belonging to group 1 or 2 of the periodic table suchas Li or Cs, which are alkali metal, Mg, Ca, or Sr, which arealkali-earth metal; an alloy (Mg:Ag or Al:Li) or a compound (LiF, CsF,or CaF₂) containing the above element. In addition, the cathode can alsobe formed from transition metal containing rare-earth metal. Further, amultilayer formed of the above material and metal (including an alloy)such as Al, Ag, or ITO can be used. In this Embodiment Mode, the cathodeis formed from aluminum.

Note that a buffer layer may be formed in the light-emitting element.Refer to Embodiment Mode 1 for the explanation of the buffer layer.

Note that in this Embodiment Mode, the anode is electrically in contactwith the conductive film 136 of the driving TFT for the light-emittingelement. Alternatively, the cathode may be electrically in contact withthe conductive film 136.

Thereafter, a silicon nitride film containing oxygen may be formed as apassivation film by a plasma CVD method. In the case of using thesilicon nitride film containing oxygen, a silicon nitride filmcontaining oxygen formed from SiH₄, N₂O, and NH₃, a silicon nitride filmcontaining oxygen formed from SiH₄ and N₂O, or a silicon nitride filmcontaining oxygen formed from a gas in which SiH₄ and N₂O are dilutedwith Ar may be deposited by a plasma CVD method.

Alternatively, a silicon oxynitride hydride film formed from SiH₄, N₂O,and H₂ may be used as the passivation film. Naturally, a structure ofthe passivation film is not limited to a single layer structure. Thepassivation film may have a single layer structure or a laminatedstructure of another insulating film containing silicon. In addition, amultilayer film of a carbon nitride film and a silicon nitride film, amultilayer film of styrene polymer, a silicon nitride film, or a diamondlike carbon film may be formed as a substitute for a silicon nitridefilm containing oxygen.

The passivation film can suppress the entrance of elements which promotedeterioration of a light-emitting element from the top surface of thelight-emitting element; thus the reliability is improved.

Subsequently, in order to protect the light-emitting element from adeterioration-promoting material such as water, the display portion issealed (FIG. 16D). In the case of using an opposite substrate 145 forsealing, the opposite substrate is attached by an insulating sealingmaterial 144. The space between the opposite substrate 145 and theelement substrate may be filled with inert gas such as dry nitrogen;alternatively, the sealing material may be applied to the entire surfaceof the pixel portion for attaching the opposite substrate 145. It ispreferable to use an ultraviolet curable resin or the like as thesealing material 144. A drying agent or particles for keeping the gapbetween the substrates uniform may be mixed into the sealing material144.

A light-emitting device thus manufactured has few defects caused byunevenness under a light-emitting element. Further, a planarizing filmis not in contact with external atmosphere, and water does not penetratethrough the planarizing film; therefore, the light-emitting device hashigh reliability.

Embodiment Mode 8

A method for manufacturing a display device of the present invention,which is different from those of Embodiment Modes 1 to 7, will bedescribed with reference to FIGS. 17 and 18. The processing steps arehalfway the same as those of Embodiment Mode 7; thus, the descriptionand diagrams are omitted. Refer to Embodiment Mode 7. FIG. 17Acorresponds to FIG. 15B.

After manufacturing up to the state shown in FIG. 15A, a planarizingfilm 230 is formed to cover a second interlayer insulating film 220. Asa material of the planarizing film 230, an application film with aself-planarizing property that can relieve unevenness formed in thelower layer by forming the film, for example, acrylic, polyimide, orsiloxane is preferably used. That is, a material that can form a filmhaving unevenness smaller than that formed in the lower layer can bepublicly employed. In addition, a film of which unevenness is relievedby reflowing or polishing the film once formed may be used. In thisEmbodiment Mode, the planarizing film 230 is formed from polyimide. Thisinsulating film having a self-planarizing property such as polyimide isapplied; thus, it is possible to relieve unevenness due to a reflectionof ridges of semiconductor layers 103 and 104, a slight unevenness ofthe interlayer insulating film, and unevenness of the lower layergenerated such as in forming conductive films 132 to 136 to be a wiringand source or drain electrodes, and to perform planarization.

Subsequently, a conductive film having a light transmitting property isformed to cover the planarizing film 230, and then a first electrode(anode) 232 of a thin film light-emitting element is formed byprocessing the conductive film having a light transmitting property withthe use of a mask 231 of resist or the like (FIG. 17B). As a material ofthe first electrode (anode) 232, metal, an alloy, an electricallyconductive compound each of which has high work function (work functionof 4.0 eV or more), a mixture of these, or the like is preferably used.For example, ITO (indium tin oxide), ITO containing silicon (ITSO), IZO(indium zinc oxide) in which zinc oxide (ZnO) is mixed by 2 to 20 atomic% into indium oxide, zinc oxide, GZO (gallium zinc oxide) in whichgallium is mixed into zinc oxide, gold (Au), platinum (Pt), nickel (Ni),tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co),copper (Cu), palladium (Pd), or metal nitride (TiN) can be used. In thisEmbodiment Mode, ITSO is used as the first electrode (anode) 232.

Next, a contact hole reaching to the conductive film 136 is opened inthe planarizing film 230 and the second interlayer insulating film 220(FIG. 17C). The contact hole can be formed by etching with the use of amask 233 of resist or the like until the conductive film 136 is exposed.Either wet etching or dry etching can be employed.

Subsequently, the mask 233 is removed, and then a conductive film isformed to cover the contact hole and the second interlayer insulatingfilm 220. The conductive film is processed into a predetermined shapeusing a mask of resist or the like in order to form such as a wiring 234electrically connected to the conductive film 136 and the firstelectrode (anode) 232 (FIG. 17C). A single metal such as aluminum orcopper, a metal alloy typified by an aluminum alloy such as an alloy ofaluminum, carbon and titanium, an alloy of aluminum, carbon and nickel,or an alloy of aluminum, carbon and titanium, a compound, or the likemay be used for forming this conductive film. The conductive film may beformed of a single layer; however, in this Embodiment Mode, thisconductive film is a laminated structure of molybdenum, aluminum andmolybdenum in this order from the bottom. In addition, a laminatedstructure formed of titanium, aluminum and titanium; titanium, titaniumnitride, aluminum and titanium; titanium and an aluminum alloy, or thelike may be employed.

After forming the wiring 234, the planarizing film 230 is removed byetching with the use of the wiring 234 and the mask of resist or thelike as masks without removing the mask of resist or the like (FIG.17D). By removing the planarizing film 230 in this processing step, theplanarizing film 230 corresponding to the first electrode (anode) 232remains; thus, planarization is realized under the first electrode(anode) 232, which is a portion in which the light-emitting element isformed; on the other hand, the planarizing film 230 corresponding to theother portion is removed. Therefore, the planarizing film is not exposedoutside a sealant forming region, and the planarizing film 230 is notexposed to external atmosphere. Accordingly, penetration of water intothe inside of a panel through the planarizing film 230 is muchdecreased, and it is possible to decrease deterioration of thelight-emitting element due to water. In addition, the planarizing film230 remains under the first electrode (anode) 232 of the light-emittingelement; thus, planarization is realized, and a defect caused byunevenness under the light-emitting element can be decreased. Note thatit is desirable that unevenness of the first electrode of thelight-emitting element is 30 nm or less in a P−V value of one pixel,preferably 15 nm or less, more preferably 10 nm or less. When theunevenness of the first electrode belongs to the above range in the P−Vvalue of one pixel, an increasing type defect can be greatly decreased.

In this processing step, a new special mask is not required; the wiring234 and the mask of resist or the like used in manufacturing the anodeare used. Therefore, it is unnecessary to further increase a processingstep such as photolithography, and planarization of the anode isrealized without increasing processing steps considerably.

A light-emitting device manufactured with the thus formed elementsubstrate in which the first electrode (anode) 232 is used as a firstelectrode of a light-emitting element has few defects caused byunevenness under the light-emitting element. Further, since water doesnot penetrate from external atmosphere through a planarizing film, thelight-emitting device has high reliability. Hereinafter, an example of amanufacturing method of a light-emitting element and a display deviceusing the first electrode (anode) 232 fabricated by following thisEmbodiment Mode is shown. Needless to say, the manufacturing method of alight-emitting element and a display device is not limited to this.

An insulating film is formed of an organic or inorganic material tocover the second interlayer insulating film 220 and the first electrode(anode) 232. Subsequently, the insulating film is processed to exposepart of the first electrode (anode) 232, thereby forming a partitionwall 141 (FIG. 18A). As a material of the partition wall 141, aphotosensitive organic material (acrylic, polyimide, or the like) ispreferably used; however, a non-photosensitive organic material or aninorganic material may also be used. Further, the partition wall 141 maybe used as a black matrix by making the partition wall 141 black in sucha way that a black pigment or dye such as titanium black or carbonnitride is diffused into the material of the partition wall 141 with theuse of a diffuse material or the like. It is desirable that thepartition wall 141 has a tapered shape in its end surface toward thefirst electrode (anode) 232 with its curvature changing continuously.

Note that it is desirable that an angle formed by the end surface of thepartition wall 141 toward the first electrode 232 side and the firstelectrode 232 is approximately 45±5°. Photosensitive polyimide is usedas the material of the partition wall 141 in order to obtain such ashape; specifically, the film thickness is approximately 1.0 μm, thetemperature of baking performed after exposing to light and developingfor patterning is approximately 300° C., thereby obtaining a preferableangle of approximately 43°. In addition, if a processing step in whichexposure is performed on the entire surface again before baking isperformed and after exposing to light and developing for patterning isadded, it is possible to make the angle smaller.

Subsequently, a light-emitting laminated body 142 is formed to cover thefirst electrode (anode) 232 exposed from the partition wall 141. Thelight-emitting laminated body 142 may be formed by a vapor depositionmethod, a spin coating method, an ink-jet method, or the like.Subsequently, a second electrode (cathode) 143 is formed to cover thelight-emitting laminated body 142 (FIG. 18B). Accordingly, alight-emitting element including the first electrode (anode) 232, thelight-emitting laminated body 142, and the second electrode (cathode)143 can be manufactured. As a cathode material for forming the secondelectrode (cathode) 143, it is preferable to use metal, an alloy, anelectrically conductive compound, each of which has low work function(work function of 3.8 eV or less), a mixture of these, or the like. Notethat as specific examples of the cathode material, the following can begiven: an element belonging to group 1 or 2 of the periodic table suchas Li or Cs, which are alkali metal, Mg, Ca, or Sr, which arealkali-earth metal; an alloy (Mg:Ag or Al:Li) or a compound (LiF, CsF,or CaF₂) containing the above element. In addition, the cathode can alsobe formed from transition metal containing rare-earth metal. Further, amultilayer formed of the above material and metal (including an alloy)such as Al, Ag, or ITO can be used. In this Embodiment Mode, the cathodeis formed from aluminum.

Note that a buffer layer may be formed in the light-emitting element.Refer to Embodiment Mode 1 for the explanation of the buffer layer.

Note that in this Embodiment Mode, the anode is electrically in contactwith the conductive film 136 of the driving TFT for the light-emittingelement. Alternatively, the cathode may be electrically in contact withthe conductive film 136.

Thereafter, a silicon nitride film containing oxygen may be formed as apassivation film by a plasma CVD method. In the case of using thesilicon nitride film containing oxygen, a silicon nitride filmcontaining oxygen formed from SiH₄, N₂O, and NH₃, a silicon nitride filmcontaining oxygen formed from SiH₄ and N₂O, or a silicon nitride filmcontaining oxygen formed from a gas in which SiH₄ and N₂O are dilutedwith Ar may be deposited by a plasma CVD method.

Alternatively, a silicon nitride film containing hydrogen and oxygenformed from SiH₄, N₂O, and H₂ may be used as the passivation film.Naturally, a structure of the passivation film is not limited to asingle layer structure. The passivation film may have a single layerstructure or a laminated structure of another insulating film containingsilicon. In addition, a multilayer film of a carbon nitride film and asilicon nitride film, a multilayer film of styrene polymer, a siliconnitride film, or a diamond like carbon film may be formed as asubstitute for a silicon nitride film containing oxygen.

The passivation film can suppress the entrance of elements which promotedeterioration of a light-emitting element from the top surface of thelight-emitting element; thus the reliability is improved.

Subsequently, in order to protect the light-emitting element from adeterioration-promoting material such as water, the display portion issealed (FIG. 18C). In the case of using an opposite substrate 145 forsealing, the opposite substrate is attached by an insulating sealingmaterial 144. The space between the opposite substrate 145 and theelement substrate may be filled with inert gas such as dry nitrogen;alternatively, the sealing material may be applied to the entire surfaceof the pixel portion for attaching the opposite substrate 145. It ispreferable to use an ultraviolet curable resin or the like as thesealing material 144. A drying agent or particles for keeping the gapbetween the substrates uniform may be mixed into the sealing material144.

A light-emitting device thus manufactured has few defects caused byunevenness under a light-emitting element. Further, a planarizing filmis not in contact with external atmosphere, and water does not penetratethrough the planarizing film; therefore, the light-emitting device hashigh reliability.

Embodiment Mode 9

A method for manufacturing a display device of the present invention,which is different from those of Embodiment Modes 1 to 8, will bedescribed with reference to FIGS. 19 and 20. The processing steps arehalfway the same as those of Embodiment Mode 1; thus, the descriptionand diagrams are omitted. Refer to Embodiment Mode 1. FIG. 19Acorresponds to FIG. 2D.

After manufacturing up to the state shown in FIG. 19A, a mask 131 isremoved, and then a second interlayer insulating film 240 is formed tocover an interlayer insulating film 129 and conductive films 132 to 136.As a material for forming the second interlayer insulating film 240, aninorganic insulating film such as silicon oxide, silicon nitride, or aLow-k material may be used. In this Embodiment Mode, a silicon oxidefilm is formed as the second interlayer insulating film 240 (FIG. 19B).

Subsequently, an extremely thin planarizing film 241 is formed to coverthe second interlayer insulating film 240. As a material of theplanarizing film 241, an application film with a self-planarizingproperty that can relieve unevenness formed in the lower layer byforming the film, for example, acrylic, polyimide, or siloxane ispreferably used. That is, a material that can form a film havingunevenness smaller than that formed in the lower layer can be publiclyemployed. In addition, a film of which unevenness is relieved byreflowing or polishing the film once formed may be used. In thisEmbodiment Mode, the planarizing film 241 is formed from acrylic. Thisinsulating film having a self-planarizing property such as acrylic isapplied; thus, it is possible to relieve unevenness due to a reflectionof ridges of semiconductor layers 103 and 104, a slight unevenness ofthe interlayer insulating film, and unevenness of the lower layergenerated such as in forming the conductive films 132 to 136, and toperform planarization.

Next, a contact hole reaching to the conductive film 136 is opened inthe planarizing film 241 and the second interlayer insulating film 240(FIG. 19C). The contact hole can be formed by etching with the use of amask 242 of resist or the like until the conductive film 136 is exposed.Either wet etching or dry etching can be employed.

Subsequently, the mask 242 is removed, and then a conductive film isformed to cover the contact hole and the planarizing film 241. Theconductive film is processed into a predetermined shape using a mask ofresist or the like in order to form a wiring 243 electrically connectedto the conductive film 136 (FIG. 19D). A single metal such as aluminumor copper, a metal alloy typified by an aluminum alloy such as an alloyof aluminum, carbon and titanium, an alloy of aluminum, carbon andnickel, or an alloy of aluminum, carbon and titanium, a compound, or thelike may be used for forming this conductive film. The conductive filmmay be formed of a single layer; however, in this Embodiment Mode, thisconductive film is a laminated structure of molybdenum, aluminum andmolybdenum in this order of manufacture. In addition, a laminatedstructure formed of titanium, aluminum and titanium; titanium, titaniumnitride, aluminum and titanium; titanium and an aluminum alloy, or thelike may be employed.

Subsequently, a conductive film having a light transmitting property isformed to cover the planarizing film 241 and the wiring 243, and then afirst electrode (anode) 245 of a thin film light-emitting element isformed by processing the conductive film having a light transmittingproperty with the use of a mask 244 of resist or the like (FIG. 20A). Asa material of the first electrode (anode) 245, metal, an alloy, anelectrically conductive compound each of which has high work function(work function of 4.0 eV or more), a mixture of these, or the like ispreferably used. For example, ITO (indium tin oxide), ITO containingsilicon (ITSO), IZO (indium zinc oxide) in which zinc oxide (ZnO) ismixed by 2 to 20 atomic % into indium oxide, zinc oxide, GZO (galliumzinc oxide) in which gallium is mixed into zinc oxide, gold (Au),platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum(Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or metalnitride (TiN) can be used. In this Embodiment Mode, ITSO is used as thefirst electrode (anode) 245.

A light-emitting device manufactured with the thus formed elementsubstrate in which the first electrode (anode) 245 is used as a firstelectrode of a light-emitting element has few defects caused byunevenness under the light-emitting element. Further, since water hardlypenetrates from external atmosphere through a planarizing film due tothe extremely thin planarizing film 241, the reliability is high.Hereinafter, an example of a manufacturing method of a light-emittingelement and a display device using the first electrode (anode) 245fabricated by following this Embodiment Mode is shown. Needless to say,the manufacturing method of a light-emitting element and a displaydevice is not limited to this. Note that it is desirable that unevennessof the first electrode of the light-emitting element is 30 nm or less ina P−V value of one pixel, preferably 15 nm or less, more preferably 10nm or less. When the unevenness of the first electrode is 30 nm or lessin a P−V value of one pixel, preferably 15 nm or less, more preferably10 nm or less, an increasing type defect can be greatly decreased.

Subsequently, an insulating film is formed of an organic or inorganicmaterial to cover the planarizing film 241 and the first electrode(anode) 245. Subsequently, the insulating film is processed to exposepart of the first electrode (anode) 245, thereby forming a partitionwall 141 (FIG. 20B). As a material of the partition wall 141, aphotosensitive organic material (acrylic, polyimide, or the like) ispreferably used; however, a non-photosensitive organic material or aninorganic material may also be used. Further, the partition wall 141 maybe used as a black matrix by making the partition wall 141 black in sucha way that a black pigment or dye such as titanium black or carbonnitride is diffused into the material of the partition wall 141 with theuse of a diffuse material or the like. It is desirable that thepartition wall 141 has a tapered shape in its end surface toward thefirst electrode 245 with its curvature changing continuously.

Note that it is desirable that an angle formed by the end surface of thepartition wall 141 toward the first electrode 245 side and the firstelectrode 245 is approximately 45±5°. Photosensitive polyimide is usedas the material of the partition wall 141 in order to obtain such ashape; specifically, the film thickness is approximately 1.0 μm, thetemperature of baking performed after exposing to light and developingfor patterning is approximately 300° C., thereby obtaining a preferableangle of approximately 43°. In addition, if a processing step in whichexposure is performed on the entire surface again before baking isperformed and after exposing to light and developing for patterning isadded, it is possible to make the angle smaller.

Subsequently, a light-emitting laminated body 142 is formed to cover thefirst electrode (anode) 245 exposed from the partition wall 141. Thelight-emitting laminated body 142 may be formed by a vapor depositionmethod, a spin coating method, an ink-jet method, or the like.Subsequently, a second electrode (cathode) 143 is formed to cover thelight-emitting laminated body 142 (FIG. 20C). Accordingly, alight-emitting element including the first electrode (anode) 245, thelight-emitting laminated body 142, and the second electrode (cathode)143 can be manufactured. As a cathode material for forming the secondelectrode (cathode) 143, it is preferable to use metal, an alloy, anelectrically conductive compound, each of which has low work function(work function of 3.8 eV or less), a mixture of these, or the like. Notethat as specific examples of the cathode material, the following can begiven: an element belonging to group 1 or 2 of the periodic table suchas Li or Cs, which are alkali metal, Mg, Ca, or Sr, which arealkali-earth metal; an alloy (Mg:Ag or Al:Li) or a compound (LiF, CsF,or CaF₂) containing the above element. In addition, the cathode can alsobe formed from transition metal containing rare-earth metal. Further, amultilayer formed of the above material and metal (including an alloy)such as Al, Ag, or ITO can be used. In this Embodiment Mode, the cathodeis formed from aluminum.

Note that a buffer layer may be formed in the light-emitting element.Refer to Embodiment Mode 1 for the explanation of the buffer layer.

Note that in this Embodiment Mode, the anode is electrically in contactwith the conductive film 136. Alternatively, the cathode may beelectrically in contact with the conductive film 136.

Thereafter, a silicon nitride film containing oxygen may be formed as apassivation film by a plasma CVD method. In the case of using thesilicon nitride film containing oxygen, a silicon nitride filmcontaining oxygen formed from SiH₄, N₂O, and NH₃, a silicon nitride filmcontaining oxygen formed from SiH₄ and N₂O, or a silicon nitride filmcontaining oxygen formed from a gas in which SiH₄ and N₂O are dilutedwith Ar may be deposited by a plasma CVD method.

Alternatively, a silicon nitride film containing hydrogen and oxygenformed from SiH₄, N₂O, and H₂ may be used as the passivation film.Naturally, a structure of the passivation film is not limited to asingle layer structure. The passivation film may have a single layerstructure or a laminated structure of another insulating film containingsilicon. In addition, a multilayer film of a carbon nitride film and asilicon nitride film, a multilayer film of styrene polymer, a siliconnitride film, or a diamond like carbon film may be formed as asubstitute for a silicon nitride film containing oxygen.

The passivation film can suppress the entrance of elements which promotedeterioration of a light-emitting element from the top surface of thelight-emitting element; thus the reliability is improved.

Subsequently, in order to protect the light-emitting element from adeterioration-promoting material such as water, the display portion issealed (FIG. 20D). In the case of using an opposite substrate 145 forsealing, the opposite substrate is attached by an insulating sealingmaterial 144. The space between the opposite substrate 145 and theelement substrate may be filled with inert gas such as dry nitrogen;alternatively, the sealing material may be applied to the entire surfaceof the pixel portion for attaching the opposite substrate 145. It ispreferable to use an ultraviolet curable resin or the like as thesealing material 144. A drying agent or particles for keeping the gapbetween the substrates uniform may be mixed into the sealing material144.

A light-emitting device thus manufactured has few defects caused byunevenness under a light-emitting element. Further, a planarizing filmis not in contact with external atmosphere, and water does not penetratethrough the planarizing film; therefore, the light-emitting device hashigh reliability.

Embodiment Mode 10

In this Embodiment Mode, an appearance of a panel of a light-emittingdevice manufactured in accordance with any one of Embodiment Modes 1 to4 will be described with reference to FIG. 24. FIG. 24A is a top view ofa panel in which a transistor and a light-emitting element formed over asubstrate are sealed with a sealing material formed between thesubstrate and an opposite substrate 4006. FIG. 24B corresponds to across-sectional view of FIG. 24A.

A sealing material 4005 is provided to surround a pixel portion 4002, asignal line driver circuit 4003, and a scanning line driver circuit 4004which are provided over a substrate 4001. The opposite substrate 4006 isprovided over the pixel portion 4002, the signal line driver circuit4003, and the scanning line driver circuit 4004. Thus, the pixel portion4002, the signal line driver circuit 4003, and the scanning line drivercircuit 4004 are sealed with the substrate 4001, the sealing material4005, and the opposite substrate 4006.

The pixel portion 4002, the signal line driver circuit 4003, and thescanning line driver circuit 4004 which are provided over the substrate4001 have a plurality of thin film transistors. A thin film transistor4008 included in the signal line driver circuit 4003 and a thin filmtransistor 4010 included in the pixel portion 4002 are shown in FIG.24B. Note that a planarizing film 4021 is shown under source and drainelectrodes of the thin film transistors 4008 and 4010 and a pixelelectrode. In this Embodiment Mode, a structure in which a planarizingfilm is provided under source and drain electrodes and a pixel electrodeis shown; however, a planarizing film may be provided following theother structures shown in Embodiment Modes 1 to 9.

Further, a light-emitting element 4011 is electrically connected to thethin film transistor 4010.

A lead wiring 4014 corresponds to a wiring for supplying signals orpower voltage by layers to the pixel portion 4002, the signal linedriver circuit 4003, and the scanning line driver circuit 4004. In aconnection terminal portion 4016, the lead wiring 4014 is electricallyconnected to a flexible printed circuit (FPC) 4018 through ananisotropic conductive film 4019.

Note that either an analog video signal or a digital video signal may beused for such a light-emitting device having a display function. In thecase of using a digital video signal, the video signal can be dividedinto a video signal using voltage and a video signal using current. Avideo signal, inputted to a pixel when a light-emitting element emitslight, includes a constant voltage video signal and a constant currentvideo signal. The constant voltage video signal includes a signal inwhich voltage applied to a light-emitting element is constant and asignal in which current applied to a light-emitting element is constant.The constant current video signal includes a signal in which voltageapplied to a light-emitting element is constant and a signal in whichcurrent applied to a light-emitting element is constant. Drive withsignal in which voltage applied to a light-emitting element is constantis constant voltage drive, and that with the signal in which currentapplied to a light-emitting element is constant is constant currentdrive. By constant current drive, constant current is applied to alight-emitting element, regardless of a change in resistance of thelight-emitting element. For a light-emitting display device of theinvention and a driving method thereof, either of the above describeddriving methods may be used.

Note that a display device of the invention includes, in its category, apanel provided with a pixel portion having a light-emitting element anda module in which an IC is mounted on the panel.

Such a panel and a module of this Embodiment Mode have few defectscaused by unevenness under a light-emitting element. Further, sincewater hardly penetrates from external atmosphere through a planarizingfilm, the panel and the module also have high reliability.

Embodiment Mode 11

Examples of an electronic device mounted with a module manufactured inaccordance with the present invention, one example of which is describedin Embodiment Mode 10, can be cited as follows: a video camera, adigital camera, a goggle type display (head mounted display), anavigation system, an sound reproducing device (a car audio component orthe like), a computer, a game machine, a portable information terminal(a mobile computer, a cellular phone, a portable game machine, anelectronic book, or the like), an image reproducing device including arecording medium (specifically, a device capable of reproducing arecording medium such as a Digital Versatile Disc (DVD) and having adisplay that can display the image), and the like. Specific examples ofthese electronic devices are shown in FIG. 23.

FIG. 23A shows a light-emitting display device. A television receiver, amonitor of a personal computer, or the like is regarded as thelight-emitting display device. The light-emitting display deviceincludes a chassis 2001, a display portion 2003, a speaker portion 2004,and the like. This invention is applied in manufacturing the displayportion 2003, and a display device having few defects caused byunevenness under a light-emitting element can be obtained. Further,since water hardly penetrates from external atmosphere through aplanarizing film, the display device has high reliability. A pixelportion is preferably provided with a polarizing plate or a circularlypolarizing plate to enhance contrast. For example, a sealing substratemay be provided with a film in this order of a quarter-wave plate, ahalf-wave plate, and a polarizing plate. Further, an anti-reflectivefilm may be provided over the polarizing plate.

FIG. 23B shows a cellular phone, which includes a main body 2101, achassis 2102, a display portion 2103, an audio input portion 2104, anaudio output portion 2105, an operation key 2106, an antenna 2108, andthe like. This invention is applied in manufacturing the display portion2103, and a cellular phone having few defects caused by unevenness undera light-emitting element can be obtained. Further, since water hardlypenetrates from external atmosphere through a planarizing film, thecellular phone has high reliability.

FIG. 23C shows a computer, which includes a main body 2201, a chassis2202, a display portion 2203, a keyboard 2204, an external connectionport 2205, a pointing mouse 2206, and the like. This invention isapplied in manufacturing the display portion 2203, and a notebookcomputer having few defects caused by unevenness under a light-emittingelement can be obtained. Further, since water hardly penetrates fromexternal atmosphere through a planarizing film, the notebook computerhas high reliability. Although a notebook computer is shown in FIG. 23Cas an example, the invention can be applied to a desktop computer inwhich a hard disk and a display portion are integrated, or the like.

FIG. 23D shows a mobile computer, which includes a main body 2301, adisplay portion 2302, a switch 2303, operation keys 2304, an infraredport 2305, and the like. This invention is applied in manufacturing thedisplay portion 2302, and a mobile computer having few defects caused byunevenness under a light-emitting element can be obtained. Further,since water hardly penetrates from external atmosphere through aplanarizing film, the mobile computer has high reliability.

FIG. 23E shows a portable gaming machine, which includes a chassis 2401,a display portion 2402, a speaker portion 2403, operation keys 2404, arecording medium insertion portion 2405, and the like. This invention isapplied in manufacturing the display portion 2402, and a portable gamingmachine having few defects caused by unevenness under a light-emittingelement can be obtained. Further, since water hardly penetrates fromexternal atmosphere through a planarizing film, the portable gamingmachine has high reliability.

As described above, the applicable range of the invention is so widethat the invention can be applied in manufacturing electronic devices ofvarious fields.

Embodiment Mode 12

A structure of the light-emitting laminated body 142 will be describedin detail in this Embodiment Mode.

A light-emitting layer may be formed of a charge injection transportmaterial and a light-emitting material which include an organic compoundor an inorganic compound. The light-emitting layer includes one or morekinds of layers of a low molecular weight organic compound, anintermediate molecular weight organic compound (referring to an organiccompound which does not have a sublimation property and has the numberof molecules of 20 or less, or a molecular chain length of 10 μm orless), and a high molecular weight organic compound, which areclassified depending on the number of molecules. The light-emittinglayer may be combined with an electron injection transport or holeinjection transport inorganic compound.

As a particularly highly electron-transporting material among chargeinjection transport materials, a metal complex that has a quinolineskeleton or a benzoquinoline skeleton such astris(8-quinolinolato)aluminum (abbreviation: Alq₃),tris(5-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: BeBq₂), orbis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbreviation:BAlq), or the like can be given. As a highly hole-transporting material,an aromatic amine-based compound (that is, a compound having a benzenering-nitrogen bond) such as4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (abbreviation: α-NPD),4,4′-bis[N-(3-methylphenyl)-N-phenyl-amino]-biphenyl (abbreviation:TPD), 4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine (abbreviation:TDATA), or4,4′,4″-tris[N-(3-methylphenyl)-N-phenyl-amino]-triphenylamine(abbreviation: MTDATA) can be given.

As a particularly highly electron-injecting material among chargeinjection transport materials, a compound of alkali metal oralkali-earth metal such as lithium fluoride (LiF), cesium fluoride (CsF)or calcium fluoride (CaF₂) can be given. In addition, a mixture of ahighly electron-transporting material such as Alq₃ and alkali-earthmetal such as magnesium (Mg) may be employed.

As a highly hole-injecting material among charge injection transportmaterials, metal oxide such as molybdenum oxide (MoOx), vanadium oxide(VOx), ruthenium oxide (RuOx), tungsten oxide (WOx), or manganese oxide(MnOx) can be given. In addition, phthalocyanine (abbreviation: H₂Pc) ora phthalocyanine-based compound such as copper phthalocyanine (CuPc) canbe given.

The light-emitting layer may have a structure for performing colordisplay by providing each pixel with a light-emitting layer having adifferent emission wavelength band. Typically, a light-emitting layercorresponding to each color of R (red), G (green), or B (blue) isformed. Also in this case, color purity can be increased and a pixelportion can be prevented from having a mirror surface (glare) byproviding a light-emitting side of a pixel with a filter (colored layer)which transmits light of its emission wavelength band. Providing afilter (colored layer) can omit a circularly polarizing plate or thelike which is conventionally required and can eliminate loss of lightemitted from a light-emitting layer. Further, a change in hue, whichoccurs when a pixel portion (display screen) is obliquely seen, can bedecreased.

An emission center includes various materials. As a low molecular weightorganic light-emitting material,4-dicyanomethylene-2-methyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran(abbreviation: DCJT),4-dicyanomethylene-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran(abbreviation: DPA), periflanthene,2,5-dicyano-1,4-bis(10-methoxy-1,1,7,7-tetramethyljulolidyl-9-enyl)benzene,N,N′-dimethylquinacridone (abbreviation: DMQd), coumarin 6, coumarin545T, tris(8-quinolinolato)aluminum (abbreviation: Alq₃),9,9′-bianthryl, 9,10-diphenylanthracene (abbreviation: DPA),9,10-bis(2-naphthyl)anthracene (abbreviation: DNA), or the like can beused. Another material may also be used.

On the other hand, a high molecular weight organic light-emittingmaterial is physically stronger than a low molecular weight material andis superior in durability of an element. In addition, a high molecularweight material can be used for application; therefore, an element isrelatively easily manufactured. A structure of a light-emitting elementusing a high molecular weight organic light-emitting material isbasically the same as that of a light-emitting element using a lowmolecular weight organic light-emitting material: a cathode, an organiclight-emitting layer, and an anode are laminated. However, it isdifficult to form such a laminated structure as in the case of using alow molecular weight organic light-emitting material, when alight-emitting layer using a high molecular weight organiclight-emitting material is formed. Thus, a two-layer structure isemployed in many cases. Specifically, a laminated structure of acathode, a light-emitting layer, a hole-transporting layer, and an anodeis employed.

An emission color is determined by a material of a light-emitting layer.Therefore, a light-emitting element that emits desired light can beformed by selecting a material of a light-emitting layer. As a highmolecular weight electroluminescent material which can be used to form alight-emitting layer, a polyparaphenylene-vinylene-based material, apolyparaphenylene-based material, a polythiophen-based material, or apolyfluorene-based material can be used.

As a polyparaphenylene-vinylene-based material, a derivative ofpoly(paraphenylene vinylene) [PPV], poly(2,5-dialkoxy-1,4-phenylenevinylene) [RO-PPV], poly(2-(2′-ethyl-hexoxy)-5-methoxy-1,4-phenylenevinylene) [MEH-PPV], poly(2-(dialkoxyphenyl)-1,4-phenylene vinylene)[ROPh-PPV], or the like can be used. As a polyparaphenylene-basedmaterial, a derivative of polyparaphenylene [PPP],poly(2,5-dialkoxy-1,4-phenylene) [RO-PPP],poly(2,5-dihexoxy-1,4-phenylene), or the like can be used. As apolythiophene-based material, a derivative of polythiophene [PT],poly(3-alkylthiophene) [PAT], poly(3-hexylthiophene) [PHT],poly(3-cyclohexylthiophene) [PCHT], poly(3-cyclohexyl-4-methylthiophene)[PCHMT], poly(3,4-dicyclohexylthiophene) [PDCHT],poly[3-(4-octylphenyl)-thiophene] [POPT],poly[3-(4-octylphenyl)-2,2bithiophene] [PTOPT], or the like can be used.As the polyfluorene-based material, a derivative of polyfluorene [PF],poly(9,9-dialkylfluorene) [PDAF], poly(9,9-dioctylfluorene) [PDOF], orthe like can be used.

Note that a hole-injecting property from an anode can be enhanced byinterposing a high molecular weight organic light-emitting materialhaving a hole-transporting property between an anode and a highmolecular weight organic light-emitting material having a light-emittingproperty. A high molecular weight organic light-emitting material havinga hole-transporting property dissolved into water together with anacceptor material is generally applied by a spin coating method, or thelike. In addition, since the high molecular weight organiclight-emitting material having a hole-transporting property is insolublein an organic solvent, a laminate with the above described organiclight-emitting material having a light-emitting property can be formed.A mixture of PEDOT and camphor sulfonic acid (CSA) that serves as anacceptor material, a mixture of polyaniline [PANI] and polystyrenesulfonic acid [PSS] that serves as an acceptor material, or the like canbe used as the high molecular weight organic light-emitting materialhaving a hole-transporting property.

In addition, the light-emitting layer can be formed to emit monochromeor white light. In the case of using a white light-emitting material, afilter (colored layer) which transmits light having a specificwavelength is provided on a light-emitting side of a pixel, therebyperforming color display.

In order to form a light-emitting layer which emits white light, forexample, Alq₃, Alq₃ partially doped with Nile red that is a redlight-emitting pigment, Alq₃, p-EtTAZ, and TPD (aromatic diamine) aresequentially stacked by a vapor deposition method to obtain white light.When a light emitting layer is formed by an application method with spincoating, baking by vacuum heating is preferably performed afterapplication. For example, an aqueous solution of poly(ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) that functionsas a hole-injecting layer may be entirely applied and baked. Thereafter,a polyvinyl carbazole (PVK) solution, which functions as alight-emitting layer, doped with a light-emitting center pigment (suchas 1,1,4,4-tetraphenyl-1,3-butadiene (TPB),4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM1),Nile red, or coumarin 6) may be entirely applied and baked.

The light-emitting layer may be formed to be a single layer. A1,3,4-oxadiazole derivative (PBD) having an electron-transportingproperty may be dispersed in polyvinyl carbazole (PVK) having ahole-transporting property. Another method to obtain white lightemission is to disperse PBD of 30 wt % as an electron-transporting agentand to disperse four kinds of pigments (TPB, coumarin 6, DCM1, and Nilered) in appropriate amounts. In addition to the light-emitting elementdescribed here that provides white light emission, a light-emittingelement that provides red light emission, green light emission, or bluelight emission can be manufactured by appropriately selecting a materialof the light-emitting layer.

Note that a hole-injecting property from an anode can be enhanced byinterposing a high molecular weight organic light-emitting materialhaving a hole-transporting property between an anode and a highmolecular weight organic light-emitting material having a light-emittingproperty. A high molecular weight organic light-emitting material havinga hole-transporting property dissolved into water together with anacceptor material is generally applied by a spin coating method, or thelike. In addition, since the high molecular weight organiclight-emitting material having a hole-transporting property is insolublein an organic solvent, a laminate with the above described organiclight-emitting material having a light-emitting property can be formed.A mixture of PEDOT and camphor sulfonic acid (CSA) that serves as anacceptor material, a mixture of polyaniline [PANI] and polystyrenesulfonic acid [PSS] that serves as an acceptor material, or the like canbe used as the high molecular weight organic light-emitting materialhaving a hole-transporting property.

Further, a triplet excitation material including a metal complex or thelike as well as a singlet excitation light-emitting material may be usedfor the light-emitting layer. For example, among pixels emitting red,green, and blue light, a pixel emitting red light whose luminance isreduced by half in a relatively short time is made of a tripletexcitation light-emitting material and the rest are made of a singletexcitation light-emitting material. A triplet excitation light-emittingmaterial has a characteristic that the material has a good luminousefficiency and consumes less power to obtain the same luminance. When atriplet excitation light-emitting material is used for a red pixel, onlya small amount of current needs to be applied to a light-emittingelement. Thus, the reliability can be improved. A pixel emitting redlight and a pixel emitting green light may be formed of a tripletexcitation light-emitting material and a pixel emitting blue light maybe formed of a singlet excitation light-emitting material to achieve lowpower consumption. Low power consumption can be further achieved also byforming a light-emitting element which emits green light that has highhuman visibility with a triplet excitation light-emitting material.

A material in which a metal complex is used as a dopant is an example ofthe triplet excitation light-emitting material; a metal complex havingplatinum that is a third transition series element as a central metal, ametal complex having iridium as a central metal, and the like are known.The triplet excitation light-emitting material is not limited to theabove compounds. A compound having the above described structure andhaving an element belonging to any of groups 8 to 10 of the periodictable as a central metal can also be used.

The above described materials for forming the light-emitting layer arejust examples. A light-emitting element can be formed by appropriatelystacking each functional layer of a hole injection transport layer, ahole-transporting layer, an electron injection transport layer, anelectron-transporting layer, a light-emitting layer, anelectron-blocking layer, a hole-blocking layer, or the like. Further, amixed layer or a mixed junction may be formed by combining these layers.A layer structure of the light-emitting layer can be varied. Instead ofproviding a specific electron-injecting region or light-emitting region,modification such as simply providing an electrode for this purpose orproviding a dispersed light-emitting material is acceptable as long asit does not deviate from the scope of the invention.

A light-emitting element formed with the above described material emitslight by being biased in a forward direction. A pixel of a displaydevice formed with a light-emitting element can be driven by a simplematrix mode or an active matrix mode. In either mode, each pixel emitslight by applying a forward bias thereto in specific timing; however,the pixel is in a non light-emitting state for a certain period. Thereliability of a light-emitting element can be improved by applying areverse bias at this non light-emitting time. In a light-emittingelement, there is a deterioration in which emission intensity isdecreased under a specific driving condition or a deterioration mode inwhich a non light-emitting region is enlarged in a pixel and luminanceis apparently decreased. However, progression of deterioration can beslowed down by alternating drive in which a bias is applied both inforward and reverse directions. Thus, the reliability of alight-emitting device can be improved.

Embodiment Mode 13

A pixel circuit and a protective circuit included in the panel andmodule shown in Embodiment Mode 10, and operations thereof will bedescribed in this Embodiment Mode.

In a pixel shown in FIG. 25A, a signal line 1410 and power supply lines1411 and 1412 are arranged in a column direction and a scanning line1414 is arranged in a row direction. In addition, the pixel includes aswitching TFT 1401, a driving TFT 1403, a current control TFT 1404, acapacitor element 1402, and a light-emitting element 1405.

A pixel shown in FIG. 25C is different in a point where a gate electrodeof a driving TFT 1403 is connected to a power supply line 1412 arrangedin a row direction, but in the other points, the pixel has a similarstructure to that of the pixel shown in FIG. 25A. In other words,equivalent circuit diagrams of both of the pixels shown in FIGS. 25A and25C are the same. However, each power supply line is formed using aconductive film in a different layer when the power supply line 1412 isarranged in a column direction (FIG. 25A) and when the power supply line1412 is arranged in a row direction (FIG. 25C). Here, a wiring connectedto the gate electrode of the driving TFT 1403 is focused and the figuresare separately shown in FIGS. 25A and 25C to show that the wirings areformed in different layers.

In the pixels shown in FIGS. 25A and 25C, the driving TFT 1403 and thecurrent control TFT 1404 are connected in series in the pixel. A channellength L(1403) and a channel width W(1403) of the driving TFT 1403 and achannel length L(1404) and a channel width W(1404) of the currentcontrol TFT 1404 are preferably set to satisfyL(1403)/W(1403):L(1404)/W(1404)=5 to 6000:1.

Note that the driving TFT 1403 operates in a saturation region and has arole of controlling a value of current flowing through thelight-emitting element 1405, and the current control TFT 1404 operatesin a linear region and has a role of controlling supply of current tothe light-emitting element 1405. It is preferable, from the viewpoint ofthe manufacturing steps, that these TFTs have the same conductivitytype. In this Embodiment Mode, these TFTs are formed to be n-channelTFTs. Further, the driving TFT 1403 may be a depletion mode TFT as wellas an enhancement mode TFT. In the invention having the above structure,the current control TFT 1404 operates in a linear region, so that slightvariation in Vgs of the current control TFT 1404 does not affect a valueof current of the light-emitting element 1405. In other words, the valueof current of the light-emitting element 1405 can be determined by thedriving TFT 1403 which operates in a saturation region. In accordancewith the above described structure, luminance variation of alight-emitting element, which is caused by variation in characteristicsof TFTs, can be improved, and a display device with improved imagequality can be provided.

In pixels shown in FIGS. 25A to 25D, the switching TFT 1401 controls theinput of a video signal to the pixel. When the switching TFT 1401 isturned on, the video signal is inputted to the pixel. Then, voltage ofthe video signal is stored in the capacitor element 1402. FIGS. 25A and25C each show a structure in which the capacitor element 1402 isprovided; however, the invention is not limited thereto. When a gatecapacitor or the like can be substituted for a capacitor that can hold avideo signal, the capacitor element 1402 is not required to be provided.

The pixel shown in FIG. 25B has the same structure as that of the pixelshown in FIG. 25A except that a TFT 1406 and a scanning line 1415 areadded. In the same manner, the pixel shown in FIG. 25D has the samestructure as that of the pixel shown in FIG. 25C except that a TFT 1406and a scanning line 1415 are added.

In the TFT 1406, “on” or “off” is controlled by the scanning line 1415that is newly arranged. When the TFT 1406 is turned on, a charge held inthe capacitor element 1402 is discharged, and the current control TFT1404 is then turned off. In other words, it is possible to make a statein which current is forced not to flow through the light-emittingelement 1405 by arranging the TFT 1406. Therefore, the TFT 1406 can bereferred to as an erasing TFT. Accordingly, in the structures in FIGS.25B and 25D, a lighting period can be started simultaneously with orimmediately after the start of a writing period without waiting for thewriting of signals in all pixels. Consequently, a duty ratio can beimproved.

In a pixel shown in FIG. 25E, a signal line 1410 and a power supply line1411 are arranged in a column direction, and a scanning line 1414 isarranged in a row direction. In addition, the pixel includes a switchingTFT 1401, a driving TFT 1403, a capacitor element 1402, and alight-emitting element 1405. A pixel shown in FIG. 25F has the samestructure as that of the pixel shown in FIG. 25E except that a TFT 1406and a scanning line 1415 are added. A duty ratio can be increased byarranging the TFT 1406 also in the structure of FIG. 25F.

As described above, various pixel circuits can be adopted. It ispreferable to make a semiconductor film of the driving TFT 1403 large,specifically, in the case of forming the thin film transistor with anamorphous semiconductor film. Therefore, the above pixel circuit ispreferably a top emission type, in which luminescence from anelectroluminescent layer is emitted from a sealing substrate side.

Such an active-matrix light-emitting device is considered to beadvantageous to low voltage driving when a pixel density is increased,since each pixel is provided with a TFT.

In this Embodiment Mode, an active-matrix light-emitting device in whicheach pixel is provided with a TFT is described. However, apassive-matrix light-emitting device in which every column is providedwith a TFT can be formed. In the passive-matrix light-emitting device, aTFT is not provided for each pixel; therefore, a high aperture ratio canbe obtained. In the case of a light-emitting device which emits light toboth sides of an electroluminescent layer, transmittance can beincreased by using the passive-matrix display device.

A display device further having such a pixel circuit of this inventionhas small drive voltage, which is not increased even as the time passes,and further can have each characteristic.

A case of providing a scanning line and a signal line with a diode as aprotective circuit is described with reference to an equivalent circuitshown in FIG. 26.

In FIG. 26, a pixel portion 1500 is provided with switching TFTs 1401and 1403, a capacitor element 1402, and a light-emitting element 1405. Asignal line 1410 is provided with diodes 1561 and 1562. The diodes 1561and 1562 are manufactured following the above Embodiment Mode as in thecase of the switching TFT 1401 or 1403, and include a gate electrode, asemiconductor layer, a source electrode, a drain electrode, and thelike. The diodes 1561 and 1562 operate as a diode by connecting the gateelectrode to the drain electrode or the source electrode.

Common potential lines 1554 and 1555 connected to the diodes are formedin the same layer as the gate electrode. Therefore, a contact hole needsto be formed in a gate insulating layer to connect the gate electrode tothe source electrode or the drain electrode of the diode.

A diode provided for a scanning line 1414 also has a similar structure.

Thus, a protective diode provided for an input stage can besimultaneously formed in accordance with this invention. Note that aposition where the protective diode is formed is not limited thereto,and the protective diode can be provided between a driver circuit and apixel.

The display device of this invention having such a protective circuithas small drive voltage, which is not increased even as the time passes,and can improve the reliability as a display device.

What is claimed is:
 1. A display device comprising: a substrate; a firstinorganic insulating film over the substrate, the first inorganicinsulating film comprising a first insulating film and a secondinsulating film; a semiconductor layer over the first inorganicinsulating film; a first conductive film overlapping with thesemiconductor layer; a second inorganic insulating film over thesemiconductor layer and the first conductive film, the second inorganicinsulating film comprising a third insulating film and a fourthinsulating film; a second conductive film over the second inorganicinsulating film and electrically connected to the semiconductor layer; athird conductive film in direct contact with the second conductive film,the third conductive film being a pixel electrode; an organicplanarizing film interposed between the third conductive film and thesecond inorganic insulating film; and a sealing material on and indirect contact with a top surface of the fourth insulating film, whereina top surface of the second conductive film is not covered by theorganic planarizing film.
 2. The display device according to claim 1,wherein the organic planarizing film is generally thinner than thesecond conductive film.
 3. The display device according to claim 1,wherein the second conductive film is over the organic planarizing film.4. The display device according to claim 1, wherein the organicplanarizing film covers a side edge of the second conductive film. 5.The display device according to claim 1, further comprising a partitionwall on and in direct contact with the second conductive film.
 6. Thedisplay device according to claim 1, further comprising a partition wallon and in direct contact with the second inorganic insulating film. 7.The display device according to claim 1, further comprising a flexibleprinted circuit affixed to the substrate and functionally connected tothe first conductive film.
 8. A display device comprising: a substrate;a first inorganic insulating film over the substrate, the firstinorganic insulating film comprising a first insulating film and asecond insulating film; a semiconductor layer comprising silicon overthe first inorganic insulating film; a first conductive film overlappingwith the semiconductor layer; a second inorganic insulating film overthe semiconductor layer and the first conductive film, the secondinorganic insulating film comprising a third insulating film and afourth insulating film; a second conductive film over the secondinorganic insulating film and electrically connected to thesemiconductor layer; a third conductive film in direct contact with thesecond conductive film, the third conductive film being a pixelelectrode; an organic planarizing film interposed between the thirdconductive film and the second inorganic insulating film; and a sealingmaterial on and in direct contact with a top surface of the fourthinsulating film, wherein the first insulating film comprises silicon andnitrogen, wherein the second insulating film comprises silicon andoxygen, wherein the third insulating film comprises silicon andnitrogen, wherein the fourth insulating film comprises silicon andoxygen, and wherein a top surface of the second conductive film is notcovered by the organic planarizing film.
 9. The display device accordingto claim 8, wherein the organic planarizing film is generally thinnerthan the second conductive film.
 10. The display device according toclaim 8, wherein the second conductive film is over the organicplanarizing film.
 11. The display device according to claim 8, whereinthe organic planarizing film covers a side edge of the second conductivefilm.
 12. The display device according to claim 8, further comprising apartition wall on and in direct contact with the second conductive film.13. The display device according to claim 8, further comprising apartition wall on and in direct contact with the second inorganicinsulating film.
 14. The display device according to claim 8, furthercomprising a flexible printed circuit affixed to the substrate andfunctionally connected to the first conductive film.
 15. A displaydevice comprising: a substrate; a first inorganic insulating film overthe substrate, the first inorganic insulating film comprising a firstinsulating film and a second insulating film; a semiconductor layercomprising crystalline silicon over the first inorganic insulating film;a first conductive film overlapping with the semiconductor layer; asecond inorganic insulating film over the semiconductor layer and thefirst conductive film, the second inorganic insulating film comprising athird insulating film and a fourth insulating film; a second conductivefilm over the second inorganic insulating film and electricallyconnected to the semiconductor layer; a third conductive film in directcontact with the second conductive film, the third conductive film beinga pixel electrode; an organic planarizing film interposed between thethird conductive film and the second inorganic insulating film; and asealing material on and in direct contact with the fourth insulatingfilm, wherein the first insulating film comprises silicon and nitrogen,wherein the second insulating film comprises silicon and oxygen, whereinthe third insulating film comprises silicon and nitrogen, wherein thefourth insulating film comprises silicon and oxygen, and wherein a topsurface of the second conductive film is not covered by the organicplanarizing film.
 16. The display device according to claim 15, whereinthe organic planarizing film is generally thinner than the secondconductive film.
 17. The display device according to claim 15, whereinthe second conductive film is over the organic planarizing film.
 18. Thedisplay device according to claim 15, wherein the organic planarizingfilm covers a side edge of the second conductive film.
 19. The displaydevice according to claim 15, further comprising a partition wall on andin direct contact with the second conductive film.
 20. The displaydevice according to claim 15, further comprising a partition wall on andin direct contact with the second inorganic insulating film.
 21. Thedisplay device according to claim 15, further comprising a flexibleprinted circuit affixed to the substrate and functionally connected tothe first conductive film.